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Cisco DEVICE AND IOS BASICS

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Device connectivity Basics The series of diagrams below reveal the cable types used for various device connectivity. I. Console Connectivity to configure a switch using management host a. PC serial port to Switch Console port

b. For remote Configuration through Auxiliary interface

Aux 0

Modem

Internet cloud

Remote computer Modem

Rollover cable is being used

Catalyst Switch

Management Console

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II. Network Connection

a. To cascade same type of device use Cross-Over cable.

b. For HUB/SWICH to PC/ROUTER – straight through cable is used & Cross- over cable is used between PC – Router & Hub – Switch.

Setting up the Management Console (windows environment): First let’s setup the Hyperterminal from windows – for interfacing with the Cisco Devices and issue commands. Here we go…

Straight Through cable Cross Over cable

Switch

Router

Host

HUB

Cross Over cable

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Path to trigger the emulation software from your Desktop Click start Programs Accessories Communications Hyper Terminal

We’ll name our Session My_Lab. The next screen requires us to configure the COM port to which we are going to connect our Cisco Device.

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Next, choose the default settings, else communication will be a problem !

On clicking OK, we’ll see the below screen & we are ready to talk to our CISCO Switch/Router !

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IOS BASICS

Pressing the RETURN key takes us to the USER EXEC mode. Switch con0 is now available Press RETURN to get started. Switch> The “>” prompt denotes user exec mode. To move into Privilege mode, we use the “enable” command. Switch>enable Switch# Privilege mode is identified with the “#” symbol. “configure terminal” command takes us into the global configuration mode where we can configure global parameters like hostname etc for the entire device. Switch#configure terminal Switch(config)# To get into any specific interface mode we have use the “interface” command with relevant interface number. To configure parameters specific to interface 1 of module 0, we issue the command as shown below.

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Switch(config)#interface fastethernet 0/1 Switch(config-if)# This is the sequence with which we change modes in the forward direction. Let’s now move backwards now. Switch(config-if)#exit Switch(config)# To go one step backward we have to use the command “exit” Switch(config)#exit Switch# However, we must use the command “disable” to move from privilege to user exec mode. If we use “exit”, it’ll log us out (and we’ll again see the first message Switch con0 is now available Press RETURN to get started) Switch#disable Switch> To logout, we use the “exit” command again. Switch>exit Switch con0 is now available Press RETURN to get started NOTE : We can use ^Z to directly move backward 2 steps – from interface mode to privilege mode. Config-if# ^Z Switch# Also note that we can use “?” whenever we want to see the various commands available in a particular mode or want to find out what commands begin with a certain letter etc. This can be easily observed in the below case. Router#? Exec commands: access-enable Create a temporary Access-List entry access-profile Apply user-profile to interface access-template Create a temporary Access-List entry archive manage archive files cd Change current directory <output omitted> Router#s? (displays all commands beginning with “s”) *s=show send setup slip squeeze start-chat systat

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If we typed a wrong spelling & try to use help the output will display as “Unrecognized command”. The same message is displayed even if we try to use help when no further arguments are possible (or wrong arguments used). Look at the below examples... Router#show router ? % unrecognized command Router#show ip a % Ambiguous command: "show ip a" Router#show ? access-expression List access expression access-lists List access lists accounting Accounting data for active sessions aliases Display alias commands arp ARP table <output omitted> Another interesting aspect is that we don’t have to type the entire command. We can just type the first few letters of a command (to the extent that only one command begins with the typed letters) and press tab – the command is completed for us! (Even if we don’t complete the command, it’ll accept!) Using tab key Let‟s just type “sh” and use the tab key tab key Router#sh (tab) Router#show There are some shortcut keys that’ll help us to work with IOS faster. Their description & use is given below. Shortcut keys to access your CLI mode CTRL-A Moves the cursor to the beginning of the line CTRL-E Moves the cursor to the end of the line ESC-B Moves the cursor back one word at a time ESC-F Moves the cursor forward one word at a time CTRL-B Moves the cursor back one character at a time LEFT ARROW Moves the cursor back one character at a time CTRL-F Moves the cursor forward one character at a time RIGHT ARROW Moves the cursor forward one character at a time CTRL-P Recalls the last command UP ARROW Recalls the last command CTRL-N Recalls the most previously executed command DOWN ARROW Recalls the most previously executed command CTRL-D Deletes the character the cursor is under BACKSPACE Deletes the character preceding the cursor CTRL-R Redisplays the current line CTRL-U Erases the line completely

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CTRL-W Erases the word the cursor is under CTRL-Z Takes you from Configuration mode back to Privilege EXEC mode TAB Once you enter a few characters and hit the TAB

key, the IOS device completes the word, assuming that you typed in enough characters to make the command or parameter unique

$ When this appears at the beginning of a command line, it indicates that there are more characters to the right of the $.

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Switching Labs

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General Experiments with Basic Switch Commands Assume we are on a Switch console and the switch’s ready – we see the below message Switch con0 is now available Press RETURN to get started. (press the return key) Switch> this is our user exec mode To get into privilege mode use the command “enable” Switch>enable Switch# The prompt has changed from “>” to “#”. if you see “#” after the hostname you are in Privilege mode To get back from privilege mode to user exec mode use the command disable Switch#disable Switch> To get into global configuration mode use the following commands Switch>enable Switch#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)# This prompt indicates global configuration mode To get into specific interface mode use the following commands Switch>enable Switch#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#interface Fastethernet 0/1 Switch(config-if)# Let’s add some description to the interface fastethernet 0/1 – indicating that Host1 is connected to this interface. We do this from the specific interface mode Switch>enable Switch#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#interface Fastethernet 0/1 Switch(config-if)#description Host1 Check out this description in running configuration using the command “show running configuration” Switch#show running-config Building configuration...

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Current configuration : 130 bytes ! interface FastEthernet0/1 description Host1 no ip address end (irrelevant output omitted) Let’s see some more basic show commands. (All show commands work only in privilege mode) To view details of interfaces/particular interface use “show interfaces” (or) “show interfaces <interface type interface id> e.g. Switch#show interfaces Fa 0/1 FastEthernet0/1 is down, line protocol is down Hardware is FastEthernet,address is 000d.ed5b.49c1(bia 000d.ed5b.49c1) MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set <output omitted> We can also observe that it’s sufficient to use the first few letters of the keyword Fastethernet – once these letters identify the unique command, the balance letters needn’t be typed ! Switch#show interface vlan 1 Vlan1 is administratively down, line protocol is down Hardware is CPUInterface,address is 000d.ed5b.49c0(bia 000d.ed5b.49c0) MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set <output omitted> Switch#Show spanning-tree No spanning tree instances exist. Following is the command to see the current device configuration which is in the RAM. Switch#show running-config Building configuration... Current configuration : 866 by version 12.1 ! hostname Switch ! interface FastEthernet0/1 description Host1 no ip address <output omitted> ! interface FastEthernet0/12 no ip address ! interface Vlan1 no ip address no ip route-cache

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shutdown ! line con 0 line vty 5 15 ! End Switch#Show startup-config Building configuration... Current configuration : 866 bytes ! version 12.1 ! hostname Switch ! ! interface FastEthernet0/1 description Host1 no ip address ! ! interface FastEthernet0/12 no ip address ! interface Vlan1 no ip address no ip route-cache shutdown ! line con 0 line vty 5 15 ! end Another interesting command to view the connectivity status of various interfaces is “show interface status” Switch#show interface status Port Name Status Vlan Duplex Speed Type Fa0/1 Host1 connected 1 a-half a-10 10/100BaseTX Fa0/2 notconnect 1 auto auto 10/100BaseTX Fa0/3 notconnect 1 auto auto 10/100BaseTX Fa0/4 notconnect 1 auto auto 10/100BaseTX Fa0/5 notconnect 1 auto auto 10/100BaseTX Fa0/6 notconnect 1 auto auto 10/100BaseTX Fa0/7 notconnect 1 auto auto 10/100BaseTX Fa0/8 notconnect 1 auto auto 10/100BaseTX Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 notconnect 1 auto auto 10/100BaseTX Now, let’s see the content of the mac-address-table of our switch - after disconnecting all connected computers (no devices connected to any interface of the switch) – using the “show mac-address-table” command

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Switch#show mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- No entries are seen! Let’s connect a host (computer) to port no. 1 and generate some traffic from it. As soon as we connect the host to the switch in the port 1 the following message can be observed on the screen 02:18:06:%LINK-3-UPDOWN: Interface FastEthernet0/1, changed state to up 02:18:07: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up To generate traffic (for the switch to learn from source address of frame) we’ll ping from the host to some IP address & then execute the show mac-address-table command again. Switch2950#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0040.33a0.4bc7 Dynamic Fa0/1 Total Mac Addresses for this criterion: 1 The above table reveals the mac address of the host connected to interface fa0/1. It also reveals that this is a dynamically learnt entry. If 2 switches are interconnected directly to each other (cascading) let’s see what happens. We shall use this simple diagram for better understanding.

0000.0000.0002 0000.0000.0001 0000.0000.000A 0000.0000.000B 0000.0000.0002

F0/1 F0/2

F0/12

F0/1 F0/2

F0/12

Switch A Switch B

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Now we see Switch A’s mac address table as below SwitchA#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0000.0000.0002 Dynamic Fa0/1 1 0000.0000.0001 Dynamic Fa0/2 1 0000.0000.000A Dynamic Fa0/12 1 0000.0000.000B Dynamic Fa0/12 1 0000.0000.00B1 Dynamic Fa0/12 1 0000.0000.00B2 Dynamic Fa0/12 Total Mac Addresses for this criterion: 6 We observe that this switch reveals the cascaded switch B’s connected host mac addresses and switch B’s Base Mac address (0000.0000.00B1) & switch B’s cascade interface Fa0/12 Mac address (0000.0000.00B2) also. A similar output would be seen for switch B’s mac table (shown below). The base Mac Address is common for the entire switch while every interface of the switch has a unique Mac address of its own also. SwitchB#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0000.0000.000A Dynamic Fa0/1 1 0000.0000.000B Dynamic Fa0/2 1 0000.0000.0001 Dynamic Fa0/12 1 0000.0000.0002 Dynamic Fa0/12 1 0000.0000.00A1 Dynamic Fa0/12 1 0000.0000.00A2 Dynamic Fa0/12 Total Mac Addresses for this criterion: 4 Let’s see what “show interface status” command reveals SwitchA#show interface status Port Name Status Vlan Duplex Speed Type <output omitted> Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 Trunk 1 auto auto 10/100BaseTX SwitchB#show interface status Port Name Status Vlan Duplex Speed Type <output omitted> Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 Trunk 1 auto auto 10/100BaseTX It displays the cascade link as TRUNK. Another interesting command to view various details regarding the switch’s configuration is “show version”

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Switch#show version Cisco Internetwork Operating System Software IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(12c)EA1, RELEASE SOFTWARE (fc1) Copyright (c) 1986-2002 by cisco Systems, Inc. Compiled Sun 24-Nov-02 23:31 by antonino Image text-base: 0x80010000, data-base: 0x80562000 ROM: Bootstrap program is CALHOUN boot loader Switch uptime is 4 hours, 33 minutes System returned to ROM by power-on System image file is "flash:/c2950-i6q4l2-mz.121-12c.EA1.bin" cisco WS-C2950-12 (RC32300) processor (revision K0) with 21002K bytes of memory. Processor board ID FOC0739W1K0 Last reset from system-reset Running Standard Image 12 FastEthernet/IEEE 802.3 interface(s) 32K bytes of flash-simulated non-volatile configuration memory. Base ethernet MAC Address: 00:0D:ED:5B:49:C0 Motherboard assembly number: 73-5782-12 Power supply part number: 34-0965-01 Motherboard serial number: FOC07391MM3 Power supply serial number: PHI073402LD Model revision number: K0 Motherboard revision number: A0 Model number: WS-C2950-12 System serial number: FOC0739W1K0 Configuration register is 0xF To save our current configuration from RAM to NVRAM (startup configuration) we use the command copy running-configuration startup-configuration (Alternately the “write” command may also be used) Switch#copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] If we want to restart the switch use the following command Switch#Reload – (used to warm boot the switch) To clear all the contents of the mac table, use the below command (this will remove only dynamic entries. Static/Permanent entries will not be removed). Switch#clear mac-address-table * To delete the startup configuration, use Switch#erase startup-config To change our switch name to “Switch2950”

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Switch(config)#hostname Switch2950 Switch2950(config)# To configure secret (encrypted) password for privilege mode (password is set as “cisco1” in the below example) Switch2950(config)#enable secret cisco1 After configuring the secret password let see the output in show running-config command Switch2950#show run Building configuration... Current configuration : 939 bytes <output omitted> hostname Switch2950 ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ (this is how the encrypted password is seen) ! <output omitted> End To configure enable password for privilege mode Switch2950(config)#enable password cisco (to configure enable password for privilege mode) Switch2950#sh run Building configuration... Current configuration : 939 bytes <output omitted> hostname Switch2950 ! enable password cisco (our password is in clear text which is in readable format) ! <output omitted> end To configure the console password, the following is the sequence. Switch2950(config)#line console 0 Switch2950(config-line)#login % Login disabled on line 0, until 'password' is set Switch2950(config-line)#password cisco show running-config reveals Switch#show running-config ! line con 0 password cisco login ! <Out put omitted>

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If we restart / relogin into the switch, it asks for the password in the beginning itself Switch2950 con0 is now available Press RETURN to get started. User Access Verification Password: (here we have to supply the console 0 password to get into user exec mode) Let’s observe the whole running-config output Switch# show running-config Building configuration... Current configuration : 1154 bytes ! version 12.1 no service single-slot-reload-enable no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Switch ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ enable password cisco ! ip subnet-zero ! ! interface FastEthernet0/1 description Host1 no ip address ! interface FastEthernet0/2 no ip address ! interface FastEthernet0/3 no ip address ! interface FastEthernet0/4 no ip address ! interface FastEthernet0/5 no ip address ! interface FastEthernet0/6 no ip address ! interface FastEthernet0/7 no ip address ! interface FastEthernet0/8

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no ip address ! interface FastEthernet0/9 no ip address ! interface FastEthernet0/10 no ip address ! interface FastEthernet0/11 no ip address ! interface FastEthernet0/12 ! interface Vlan1 no ip address shutdown ! ip http server ! ! line con 0 password cisco login line vty 0 4 line vty 5 15 ! End Note: if both secret and enable passwords exist, only secret will be used to get into privilege mode. Let’s say we have some remote administrators who’ll logon into this switch remotely. (They can do so because Cisco switches run terminal services). However, setting the vty password is a must for telnet access & this is how we do it. Lets start configuring the VTY sessions Switch2950(config)#line vty 0 15 Switch2950(config-line)#login % Login disabled on line 1, until 'password' is set % Login disabled on line 2, until 'password' is set % Login disabled on line 3, until 'password' is set % Login disabled on line 4, until 'password' is set % Login disabled on line 5, until 'password' is set % Login disabled on line 6, until 'password' is set % Login disabled on line 7, until 'password' is set % Login disabled on line 8, until 'password' is set % Login disabled on line 9, until 'password' is set % Login disabled on line 10, until 'password' is set % Login disabled on line 11, until 'password' is set % Login disabled on line 12, until 'password' is set % Login disabled on line 13, until 'password' is set % Login disabled on line 14, until 'password' is set % Login disabled on line 15, until 'password' is set % Login disabled on line 16, until 'password' is set

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This reveals that 16 simultaneous telnet sessions are possible! we have to configure the password to enable all these 16 sessions Switch2950(config-line)#password cisco Switch2950(config-line)# This config alone is not sufficient for telnetting. We need to define an IP address to the switch and only then telnet is possible. Where do we configure an IP address in the switch ? Switch2950>enable Switch2950#configure terminal Switch2950(config)#interface vlan 1 Switch2950(config-if)#ip address 1.1.1.1 255.0.0.0 (this is the command to configure ip address for an interface). So, we configure the IP address to VLAN1 (we’ll learn more about vlan later). Switch2950(config-if)#no shutdown (after assigning the ip address we have enable the interface using the “NO SHUTDOWN” command). We will be able to see the below message. 01:33:27: %LINK-3-UPDOWN: Interface Vlan1, changed state to up 01:33:29: %LINK-3-UPDOWN: Interface Vlan1, Line Protocol changed state to up Let’s now see how we can control the speed & Duplex operation of the switch Switch2950(config)#interface fastethernet 0/1 Switch2950(config-if)#duplex half Note : Duplex will not be set until speed is set to non-auto value Switch2950(config-if)#speed 10 Switch2950(config-if)#duplex half Now check the out put in show interface status command Switch#show interface status Port Name Status Vlan Duplex Speed Type Fa0/1 Host1 connected 1 half 10 10/100BaseTX Fa0/2 notconnect 1 auto auto 10/100BaseTX Fa0/3 notconnect 1 auto auto 10/100BaseTX Fa0/4 notconnect 1 auto auto 10/100BaseTX Fa0/5 notconnect 1 auto auto 10/100BaseTX Fa0/6 notconnect 1 auto auto 10/100BaseTX Fa0/7 notconnect 1 auto auto 10/100BaseTX Fa0/8 notconnect 1 auto auto 10/100BaseTX Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 notconnect 1 auto auto 10/100BaseTX

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Had the switch auto negotiated, the output would have been Port Name Status Vlan Duplex Speed Type Fa0/1 Host1 connected 1 a-half a-10 10/100BaseTX Fa0/2 notconnect 1 auto auto 10/100BaseTX Fa0/3 notconnect 1 auto auto 10/100BaseTX Fa0/4 notconnect 1 auto auto 10/100BaseTX Fa0/5 notconnect 1 auto auto 10/100BaseTX Fa0/6 notconnect 1 auto auto 10/100BaseTX Fa0/7 notconnect 1 auto auto 10/100BaseTX Fa0/8 notconnect 1 auto auto 10/100BaseTX Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 notconnect 1 auto auto 10/100BaseTX a-half a-10 means auto negotiated with connected device to half duplex & 10 Mbps. PORT SECURITY : Let’s now learn how switch interfaces can be configured to allow connectivity only for pre-defined hosts (based on their Mac-Addresses). This is done on a per interface basis. Before configuring port security for the interfaces, let’s see the output of “show port-security” command Switch#show port-security Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action (Count) (Count) (Count) ----------------------------------------------------------------------- ----------------------------------------------------------------------- Total Addresses in System : 0 Max Addresses limit in System : 1024 Now let’s configure port security for interface Fa 0/1 – only system with mac id 0000.0000.a111 should be allowed connectivity – any other device connection to this interface should result in the interface shutting down. Manual port security Switch2950(config)#interface fastethernet 0/1 Switch2950(config-if)#switchport mode access Switch2950(config-if)#switchport port-security Switch2950(config-if)#switchport port-security mac-address 0000.0000.A111 See the output in show running-config & show port-security Switch2950#sh run Building configuration... Current configuration : 1089 bytes ! hostname Switch2950 ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ enable password cisco ! !

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interface FastEthernet0/1 switchport mode access switchport port-security switchport port-security mac-address 0000.0000.A111 no ip address duplex half speed 10 <output omitted> Switch2950#show port-security Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action (Count) (Count) (Count) ----------------------------------------------------------------------- Fa0/1 1 1 0 Shutdown ----------------------------------------------------------------------- Total Addresses in System : 0 Max Addresses limit in System : 1024 We can also ask the switch to auto-learn the mac address of the connected host using the keyword “sticky” Switch2950(config)#interface fastethernet 0/2 Switch2950(config-if)#switchport mode access Switch2950(config-if)#switchport port-security Switch2950(config-if)#switchport port-security mac-address sticky After configuring sticky if any traffic comes to the interface fastethernet 0/2 of the switch will learn the mac-address and secure it. Switch2950#show running-config Building configuration... Current configuration : 1089 bytes ! hostname Switch2950 ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ enable password cisco ! ! interface FastEthernet0/2 switchport mode access switchport port-security switchport port-security mac-address sticky switchport port-security mac-address 0000.0000.A112 no ip address <output ommitted> Switch2950#show port-security Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action (Count) (Count) (Count) ----------------------------------------------------------------------- Fa0/1 1 1 0 Shutdown Fa0/2 1 1 0 Shutdown ----------------------------------------------------------------------- Total Addresses in System : 0 Max Addresses limit in System : 1024

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By default, only one mac-address will be locked to the interface – this can be changed as demonstrated below. Increasing the maximum count of mac-address secured for the interface Switch2950(config)#interface fastethernet 0/3 Switch2950(config-if)#switchport mode access Switch2950(config-if)#switchport port-security Switch2950(config-if)#switchport port-security maximum 4 <0-132> Switch2950#sh run Building configuration... Current configuration : 1089 bytes ! hostname Switch2950 ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ enable password cisco ! interface FastEthernet0/3 switchport mode access switchport port-security switchport port-security maximum 4 no ip address <output omitted> Switch2950#show port-security Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action (Count) (Count) (Count) ----------------------------------------------------------------------- Fa0/1 1 1 0 Shutdown Fa0/2 1 1 0 Shutdown Fa0/3 4 0 0 Shutdown ----------------------------------------------------------------------- Total Addresses in System : 0 Max Addresses limit in System : 1024 The security action is shutdown by default & we can change this among one of 3 modes. Shutdown (default) - if violation happens interface will shutdown automatically Protect (don’t log) - if violation happens interface won’t shutdown, won’t allow for communication, won’t log any error Restrict (do log) - if violation happens interface won’t shutdown but no communication will be allowed & an alert would be sent / SNMP trap sent. The configuration may be done as shown below. Switch2950(config)#interface fastethernet 0/4 Switch2950(config-if)#switchport mode access Switch2950(config-if)#switchport port-security Switch2950(config-if)#switchport port-security violation shutdown / protect / restrict If we chose protect

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F0/11 F0/11

Switch A Switch B

1000.0000.000A 0000.0000.000A

Switch2950#sh run Building configuration... Current configuration : 1089 bytes ! hostname Switch2950 ! enable secret 5 $1$z9ZE$mO/4D6DgtZcTrmzmyX3Ys/ enable password cisco ! interface FastEthernet0/4 switchport mode access switchport port-security switchport port-security violation protect switchport port-security mac-address 0000.0000.A131 no ip address <output omitted> Switch2950#show port-security Secure Port MaxSecureAddr CurrentAddr SecurityViolation Security Action (Count) (Count) (Count) ----------------------------------------------------------------------- Fa0/1 1 1 0 Shutdown Fa0/2 1 1 0 Shutdown Fa0/3 4 0 0 Shutdown Fa0/4 1 0 0 Protect -----------------------------------------------------------------------Total Addresses in System : 0 Max Addresses limit in System : 1024 Spanning-tree protocol - L et’s n ext d o som e b asic ob servation on S T P With reference to the above diagram, the Root Bridge is Switch B because it has the lowest mac-address 0000.0000.000A. Switch A will be the non-root bridge. Let’s see the output of show spanning-tree command now. SwitchB#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0000.0000.000A This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0000.0000.000A Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300

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Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ------------ -------- --------- --- ------ -------------------------- Fa0/11 128.1 100 FWD 0 32769 1000.0000.000A 128.1 SwitchA#show spanning-tree VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0000.0000.000A This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 1000.0000.000A Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300 Interface Port ID Designated Port ID Name Prio.Nbr Cost Sts Cost Bridge ID Prio.Nbr ----------- -------- --------- --- --------- -------------------- ----- Fa0/11 128.1 100 FWD 0 32769 0000.0000.000A 128.1 The next major topic we would like to see is VLAN. The output of “show vlan” command when no vlans are configured is Switch2950#show vlan VLAN Name Status Ports ---- ------------------------ --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active VLAN Type SAID MTU Parent RingNo BridgeNo Stp BrdgMode Tran1 Tran2 ---- ----- ------ ---- ------ ------ -------- --- ------- ----- ----- 1 enet 100001 1500 - - - - - 0 0 1002 fddi 101002 1500 - - - - - 0 0 1003 tr 101003 1500 - - - - srb 0 0 1004 fdnet 101004 1500 - - - ieee - 0 0 1005 trnet 101005 1500 - - - ibm - 0 0 Remote SPAN VLANs ----------------------------------------------------------------------- Primary Secondary Type Ports ------- --------- ----------------- ----------------------------------- We can observe that all the interfaces are associated with the default VLAN1. Now let’s get on to creating STATIC VLANs & define port associations. Two possibilities exist. One from the privilege mode (using VLAN Database) & the second from global config mode.

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Creating vlan using “vlan database” method Switch2950#vlan database Switch2950(vlan)#vlan 2 name CCNA – creating VLAN with id 2 & name CCNA VLAN 2 added: Name: CCNA Switch2950(vlan)#apply – to save the configuration APPLY completed. Switch2950(vlan)#exit – implicit save & exit APPLY completed. Exiting.... Using “^Z” will not save the config & we will also exit from vlan database. After Vlan is created see the output of “show vlan” command Switch2950#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10, Fa0/11, Fa0/12 2 CCNA active 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active <output omitted> Assigning vlan membership – let’s make interface fa0/4 a member of Vlan 2 Switch2950(config)#int fastEthernet 0/4 Switch2950(config-if)#switchport mode access Switch2950(config-if)#switchport access vlan 2 Switch2950(config-if)# ^z Interface 4 is now assigned to vlan 2 Switch2950#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/5 Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10, Fa0/11, Fa0/12 2 CCNA active Fa0/4 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active <output omitted> You are seeing the output from show run command after assigning the membership for the interface 4 Switch2950#show run Building configuration...

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! Current configuration : 98 bytes ! interface FastEthernet0/4 switchport access vlan 2 switchport mode access no ip address end Let’s repeat the above using the second method - Creating vlan using global configuration mode Switch2950#configure terminal Switch2950(config)#vlan 3 Switch2950(config-vlan)#name CCNP Switch2950(config-vlan)#exit Output of show vlan command after creating vlan 3 in global configuration mode Switch2950#sh vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/5 Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10, Fa0/11, Fa0/12 2 CCNA active Fa0/4 3 CCNP active 1002 fddi-default active 1003 token-ring-default active 1004 fddinet-default active 1005 trnet-default active We can see that the outcome is the same wherever we create the VLAN from. If we wanted to know the VTP Domain name, version used, VTP switch mode, we use the command “show vtp status” Switch2950#show vtp status VTP Version : 2 Configuration Revision : 1 Maximum VLANs supported locally : 64 Number of existing VLANs : 6 VTP Operating Mode : Server VTP Domain Name : Null VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled Let’s change the switch mode to CLIENT. Switch2950#vlan database Switch2950(vlan)#vtp client Setting device to VTP CLIENT mode. The same task using global configuration mode - Switch2950#configure terminal

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Switch2950(config)#vtp mode Server / Client / Transparent Switch2950#show vtp status VTP Version : 2 Configuration Revision : 1 Maximum VLANs supported locally : 64 Number of existing VLANs : 6 VTP Operating Mode : Client VTP Domain Name : Null VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled Now we are going to change vtp domain name from “Null” to “Cisco” using vlan database method Switch2950#vlan database Switch2950(vlan)#vtp domain Cisco Changing VTP domain name from Null to Cisco Switch2950(vlan)#exit APPLY completed. Exiting.... Same task using global configuration mode Switch2950#configure terminal Switch(config)#vtp domain Cisco Changing VTP domain name from Null to Cisco Switch2950#show vtp status VTP Version : 2 Configuration Revision : 0 Maximum VLANs supported locally : 64 Number of existing VLANs : 6 VTP Operating Mode : Server VTP Domain Name : Cisco VTP Pruning Mode : Disabled VTP V2 Mode : Disabled VTP Traps Generation : Disabled

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Let’s see how mac address table reflects the vlan configuration in the below case. Switch A & B’s mac address table & interface status reveal - SwitchA#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0000.0000.0002 Dynamic Fa0/1 2 0000.0000.0001 Dynamic Fa0/2 1 0000.0000.000A Dynamic Fa0/12 2 0000.0000.000B Dynamic Fa0/12 <other entries omitted> SwitchB#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0000.0000.000A Dynamic Fa0/1 2 0000.0000.000B Dynamic Fa0/2 1 0000.0000.0001 Dynamic Fa0/12 1 0000.0000.0002 Dynamic Fa0/12 <other entries omitted>

0000.0000.0002 0000.0000.0001 0000.0000.000A 0000.0000.000B

F0/1 F0/2

F0/12

F0/1 F0/2

F0/12

Switch A Switch B

Vlan 1

Vlan 2

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SwitchA#show interface status Port Name Status Vlan Duplex Speed Type Fa0/1 connected 1 full 100 10/100BaseTX Fa0/2 connected 2 full 100 10/100BaseTX Fa0/3 notconnect 1 auto auto 10/100BaseTX Fa0/4 notconnect 1 auto auto 10/100BaseTX Fa0/5 notconnect 1 auto auto 10/100BaseTX Fa0/6 notconnect 1 auto auto 10/100BaseTX Fa0/7 notconnect 1 auto auto 10/100BaseTX Fa0/8 notconnect 1 auto auto 10/100BaseTX Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 Trunk 1 auto auto 10/100BaseTX SwitchB#show interface status Port Name Status Vlan Duplex Speed Type Fa0/1 connected 1 full 100 10/100BaseTX Fa0/2 connected 2 full 100 10/100BaseTX Fa0/3 notconnect 1 auto auto 10/100BaseTX Fa0/4 notconnect 1 auto auto 10/100BaseTX Fa0/5 notconnect 1 auto auto 10/100BaseTX Fa0/6 notconnect 1 auto auto 10/100BaseTX Fa0/7 notconnect 1 auto auto 10/100BaseTX Fa0/8 notconnect 1 auto auto 10/100BaseTX Fa0/9 notconnect 1 auto auto 10/100BaseTX Fa0/10 notconnect 1 auto auto 10/100BaseTX Fa0/11 notconnect 1 auto auto 10/100BaseTX Fa0/12 Trunk 1 auto auto 10/100BaseTX To view trunk details we use the commands “show interface <interface id> trunk” & “show interface <interface id> switchport” SwitchA#show interface fastethernet 0/12 switchport Name: Fa0/12 Switchport: Enabled Administrative Mode: dynamic desirable Operational Mode: dynamic Administrative Trunking Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 1 (default) We can even configure the mac-address statically. The following command is used. SwitchA(config)#mac-address static 0000.0000.AAAA vlan 3 interface fastEthernet 0/11 Then our mac-address table looks like this SwitchA#sh mac-address-table Mac Address Table ------------------------------------------ Vlan Mac Address Type Ports ---- ----------- ---- ----- 1 0000.0000.000A Dynamic Fa0/1 2 0000.0000.000B Dynamic Fa0/2 3 0000.0000.AAAA Static Fa0/11 1 0000.0000.0001 Dynamic Fa0/12

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1 0000.0000.0002 Dynamic Fa0/12 Total Mac Addresses for this criterion: 5

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Routing

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Static Routes There are actually two ways that a router can learn a static route. First, a router will look at its active interfaces, examine the addresses configured on the interfaces and determine the corresponding network numbers, and populate the routing table with this information. This is commonly called a connected route. The following example shows the routing table of a Router whose Ethernet 0 interface has been configured with an IP Address 10.0.0.1 & Serial 0 with 192.168.1.1. To view the Routing table, use the command “show ip route” Router_1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B –

BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route

Gateway of last resort is not set C 10.0.0.0/8 is directly connected, Ethernet0 C 192.168.1.0/24 is directly connected, Serial0 Explanation of the Routing Table Entries : The top portion of the display for this command has a table of codes. These codes, which describe a type of route that may appear in the routing table, are shown in the first column at the bottom part of the display. “C” represents that it’s a directly connected network. This is followed by Network ID & to which interface that network is connected. In 10.0.0.0/8, the “/8” represents the subnet mask – 255.0.0.0 Note : If we hadn’t configured any IP address on the router, there would be no entries in the routing table – it would have been empty.

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The second way is when we manually configure it. A static route is a manually configured route on the router. Consider the below network with IP addresses configured as shown.

Static Route Configuration To configure a static route for IP, use one of these two commands: Router(config)#ip route <Dest_Net_ID><subnet_mask><next_hop IP_address> -or- Router(config)#ip route <Dest_Net_ID>< subnet_mask>< interface_to_exit> The first parameter that you must specify is the destination network number. After the subnet mask parameter, you have two ways to specify how to reach the destination network: (i)By specifying the next hop neighbor’s IP address (safe to use this – as this is suitable for all environments) or (ii)The router’s specific exit interface to reach a destination network. (Use this method if it is a point-to-point link only). In this instance, you must specify the name of the interface on the router, like serial0. Here below is the configuration of Router R1 with the next hop neighbor’s IP address. R1#sh run Building configuration... Current configuration : 908 bytes version 12.2 (irrelevant output omitted)

S0 S0 S1 S1

E0 E0 E0

172.16.0.1 172.16.0.2

192.168.1.1 192.168.1.2

10.0.0.1 20.0.0.1 30.0.0.1

R1 R2 R3

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interface Ethernet0 ip address 10.0.0.1 255.0.0.0 ! interface Serial0 ip address 192.168.1.1 255.255.255.0 no fair-queue clockrate 64000 ! ip route 20.0.0.0 255.0.0.0 192.168.1.2 ip route 30.0.0.0 255.0.0.0 192.168.1.2 ip route 172.16.0.0 255.255.0.0 192.168.1.2 ip http server ! line con 0 transport input none line aux 0 ! end The following shows the routing table of a Router (R1 – the leftmost Router) with Static Routes configured. R1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B –

BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route

Gateway of last resort is not set S 20.0.0.0/8 [1/0] via 192.168.1.2 S 172.16.0.0/16 [1/0] via 192.168.1.2 C 10.0.0.0/8 is directly connected, Ethernet0 C 192.168.1.0/24 is directly connected, Serial0 S 30.0.0.0/8 [1/0] via 192.168.1.2 This shows additional entries (configuration discussed next) with “S” – representing manually configured static routes. Consider the entry - S 20.0.0.0/8 [1/0] via 192.168.1.2 Two values in “[1 / 0]” represent the Administrative Distance (AD) & Metric value respectively (details discussed in separate section). Suffice to remember that the first value is the AD value and its default value is “1” for a static route. The next value indicates the metric & the default value of a statically configured route is always “0”. via 192.168.1.2 represents the gateway address, i.e. the next router’s interface IP address – this is the interface through which the data has to travel from R1 to reach destination Network 20.0.0.0 (which is connected to router R2).

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Here below is the configuration of Router R2 with the exit interface configuration. R2#sh run Building configuration... Current configuration : 654 bytes (irrelevant output omitted) ! interface Ethernet0 ip address 20.0.0.1 255.0.0.0 ! interface Serial0 ip address 172.16.0.1 255.255.0.0 clockrate 64000 ! interface Serial1 ip address 192.168.1.2 255.255.255.0 ! no ip http server ip classless ip route 10.0.0.0 255.0.0.0 Serial1 ip route 30.0.0.0 255.0.0.0 172.16.0.2 ! line con 0 line aux 0 line vty 0 4 password cisco login ! ! end The following table shows the routing table of R2 R2#sh ip route Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per- user static route o - ODR, P - periodic downloaded static route Gateway of last resort is not set C 20.0.0.0/8 is directly connected, Ethernet0 C 172.16.0.0/16 is directly connected, Serial0 S 10.0.0.0/8 is directly connected, Serial1 C 192.168.1.0/24 is directly connected, Serial1 S 30.0.0.0/8 [1/0] via 172.16.0.2 In this example, there are three connected routes, and two static routes. The static route (10.0.0.0) is treated as a directly connected route, since it was created by specifying the interface to exit the router – “SERIAL1”.

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BACKUP ROUTE While configuring static route, optionally you can change the administrative distance of a static route. If you omit this value, it will have one of two defaults, depending on the configuration of the previous parameter. If you specified the next hop neighbor’s IP address, then the administrative distance defaults to 1. If you specified the interface on the router it should use to reach the destination, the router treats the route as a connected route and assigns an administrative distance of 0 to it. Please note that you can create multiple static routes to the same destination. For instance, you might have primary and backup paths to the destination. For the primary path, use the default administrative distance value. For the backup path, use a number higher than this, such as 2. Once you have configured a backup path, the router will use the primary path, and if the interface on the router fails for the primary path, the router will use the backup route. The configuration of Router R3 with the interface the router should exit to reach the destination network with a administrative distance value of 2 and also with the next hop neighbor’s IP address pointing to Router R2.

R3#sh run Building configuration... Current configuration : 725 bytes ! version 12.2 ! enable password cisco (irrelevant output omitted) ! interface Ethernet0 ip address 30.0.0.1 255.0.0.0 duplex auto speed auto ! interface Serial0 ip address 172.16.0.2 255.255.0.0 ! interface Serial1 ip address 200.0.0.2 255.255.255.0

S0 S0

S1 S1

E0 E0 E0

172.16.0.2 192.168.1.1 192.168.1.2

10.0.0.1 20.0.0.1 30.0.0.1

R1 R2 R3 200.0.0.1

200.0.0.2

S1 S0

172.16.0.1

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! ip route 20.0.0.0 255.0.0.0 172.16.0.1 ip route 20.0.0.0 255.0.0.0 Serial0 2 ip http server ! ! line con 0 logging synchronous line aux 0 line vty 0 4 password cisco login ! end

The following example shows the routing table of R3

R3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set S 20.0.0.0/8 [1/0] via 172.16.0.1 C 172.16.0.0/16 is directly connected, Serial1 C 200.0.0.0/24 is directly connected, Serial0 C 30.0.0.0/8 is directly connected, Ethernet0 Mark here that even though we have configured 20.0.0.0 network with the outgoing interface Serial0 , it has not been populated in the routing table because of higher Administrative Distance number.

Default Route Configuration A default route is a special type of static route. Where a static route specifies a path a router should use to reach a specific destination, a default route specifies a path the router should use if it doesn’t know

S0 S1

E0 E0

172.16.0.1

20.0.0.1 30.0.0.1

R2 R3

172.16.0.2

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how to reach the destination. Sometimes this is also referred to as a “gateway of last resort”. Note that if a router does not have any path in its routing table telling it how to reach a destination, and the router receives a packet destined for this network, the router will drop the packet. Therefore, a default route can serve as a catch-all: if there is no specific path to the destination, the router will use the default route to reach it. To set up a default route, use the following syntax for a static route: Router(config)#ip route 0.0.0.0 0.0.0.0 IP_address_of_next_hop_neighbor -or- Router(config)# ip route 0.0.0.0 0.0.0.0 interface_to_exit The network number of 0.0.0.0/0 represents all networks, and a mask of all 0’s in the bit position represents all hosts in the specified network. The configuration of Router R3 with a default route is shown below. R3#sh run Building configuration... (irrelevant output omitted) interface Ethernet0 ip address 30.0.0.1 255.0.0.0 duplex auto speed auto ! interface Serial1 ip address 172.16.0.2 255.255.0.0 ! ip route 0.0.0.0 0.0.0.0 Serial1 line con 0 ! end The following table shows the routing table of R3

R3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is Serial0 to network 0.0.0.0 C 172.16.0.0/16 is directly connected, Serial0 C 30.0.0.0/8 is directly connected, Ethernet0 S* 0.0.0.0/0 [1/0] via Serial0

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RIP We shall have a simple setup to learn how RIP routing is enabled and also try to find out what happens dynamically when a network change occurs. In this exercise, to emulate connected networks, we’ll create “virtual interfaces” called loopback interfaces. We’ll identify and configure clockrate on DCE interfaces. We’ll verify our IP configuration using the “show ip interface brief” command & finally enable RIP routing protocol.

1. To create a loopback interface use the “interface loopback <id>” command. This is very similar to a regular interface command – a loopback automatically gets created. Create a loopback interface in Router1 Router1(config)#int loopback 0 Router1(config-if)#ip address 1.1.1.1 255.0.0.0 Rotuer1(config-if)#exit Create a loopback interface in Router3 Rotuer3(config)#int loopback 0 Rotuer3(config-if)#ip address 3.3.3.3 255.0.0.0 Rotuer3(config-if)#exit 2. We also need to identify if the WAN serial interface is a DCE or DTE using “show controllers serial 0” command because the DCE provides clocking. Router1#sh controller s 1 HD unit 0, idb = 0x29A524, driver structure at 0x2A1AE8 buffer size 1524 HD unit 0, V.35 DTE cable cpb = 0xE1, eda = 0x4940, cda = 0x4800 RX ring with 16 entries at 0xE14800 00 bd_ptr=0x4800 pak=0x2A5AFC ds=0xE1ECC8 status=00 pak_size=0 01 bd_ptr=0x4814 pak=0x2A584C ds=0xE1E60C status=00 pak_size=0 02 bd_ptr=0x4828 pak=0x2A559C ds=0xE1DF50 status=00 pak_size=0 03 bd_ptr=0x483C pak=0x2A52EC ds=0xE1D894 status=00 pak_size=0 04 bd_ptr=0x4850 pak=0x2A503C ds=0xE1D1D8 status=00 pak_size=0 <output omitted> Rotuer3#show controllers serial 0 HD unit 0, idb = 0x2A1B80, driver structure at 0x2A9140

Router1 Router3

L 0 L 0 3.3.3.3 1.1.1.1

Serial 1 Serial 0

11.0.0.22

11.0.0.111

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buffer size 1524 HD unit 0, V.35 DCE cable cpb = 0xE2, eda = 0x2940, cda = 0x2800 RX ring with 16 entries at 0xE22800 00 bd_ptr=0x2800 pak=0x2AD158 ds=0xE2C60C status=80 pak_size=0 01 bd_ptr=0x2814 pak=0x2ACEA8 ds=0xE2BF50 status=80 pak_size=0 02 bd_ptr=0x2828 pak=0x2ACBF8 ds=0xE2B894 status=80 pak_size=0 03 bd_ptr=0x283C pak=0x2AC948 ds=0xE2B1D8 status=80 pak_size=0 04 bd_ptr=0x2850 pak=0x2AC698 ds=0xE2AB1C status=80 pak_size=0 <output omitted> The above reveals that Router3’s serial interface is the DCE end & implies that we need to configure the clockrate on Router3’s S0 interface using the “clock rate <value>” command. Router3(Config-if)#clock rate 64000 We can also view the enabled ROUTED PROTOCOL using “show protocols” command. (This reveals that IP is enabled). Rotuer3#show protocols Global values: Internet Protocol routing is enabled Ethernet0 is administratively down, line protocol is down Ethernet1 is administratively down, line protocol is down Loopback0 is up, line protocol is up Internet address is 3.3.3.3/8 Serial0 is up, line protocol is up Internet address is 11.0.0.2/8 Serial1 is administratively down, line protocol is down When no routing protocol is configured, the Routing table displays directly connected routes only (after configuring serial interface ip address also). Router3#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set C 3.0.0.0/8 is directly connected, Loopback0 C 11.0.0.0/8 is directly connected, Serial0 3. Another useful command (to view various interface status) is the “show ip interface brief”. Router1#show ip interface brief Interface IP-Address OK? Method Status Protocol

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Ethernet0 unassigned YES NVRAM administratively down down Loopback0 1.1.1.1 YES manual up up Serial0 unassigned YES NVRAM administratively down down Serial1 11.0.0.1 YES manual up up The “method” column tells us whether the interface configuration was taken from NVRAM (startup-config) or was manually configured by the administrator. The status & Protocol reveal the link (connected network) status. If status shows as up, the link is OK. If it shows as down, the network is down. If it’s administratively down, it means that the network has been manually shut down using the “shutdown” command. If protocol shows as down, it means that the line protocol is not properly configured. Typically either the encapsulation or the clock rate is not configured properly. ENABLING RIP PROTOCOL Let’s now enable the RIP Routing Protocol using “Router RIP” command & publish directly connected Networks using “Network <Network id>” command Router3(config)#router rip Router3(config-router)#Network 3.0.0.0 Router3(config-router)#Network 11.0.0.0 Router3(config-router)#end Router3# Let’s see if the above 3 configurations are reflected in the running-config output… Router3#show running-config Building configuration... Current configuration : 769 bytes ! version 12.2 no service single-slot-reload-enable service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Router3 ! logging rate-limit console 10 except errors enable password cisco ! ip subnet-zero no ip finger ! no ip dhcp-client network-discovery ! interface Loopback0 ip address 3.3.3.3 255.0.0.0 ! interface Ethernet0

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no ip address shutdown ! interface Ethernet1 no ip address shutdown ! interface Serial0 ip address 11.0.0.2 255.0.0.0 clockrate 64000 <DCE interface> ! interface Serial1 no ip address shutdown ! router rip network 3.0.0.0 network 11.0.0.0 ! ip kerberos source-interface any ip classless ip http server ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end similarly in Router1, Router1(config)#router rip Router1(config-router)#network 1.0.0.0 Router1(config-router)#network 11.0.0.0 Router1(config-router)#end Router1#show running-config Building configuration... hostname Router1 ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Ethernet0 no ip address shutdown ! interface Serial0 no ip address shutdown ! interface Serial1 ip address 11.0.0.1 255.0.0.0

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! router rip network 1.0.0.0 network 11.0.0.0 ! end <output omitted> We are clearly able to see the configuration changes in the running-config of both the routers. If we view Router1's routing table, we’ll be able to see what routes have been learnt through RIP. Router1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area* - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 R 3.0.0.0/8 [120/1] via 11.0.0.2, 00:00:05, Serial1 C 11.0.0.0/8 is directly connected, Serial1 Consider the second entry of the routing table “R” represents RIP learnt routes “[120/1]” represents AD value of 120 for RIP & hop count of 1 to reach network 3.0.0.0 “via 11.0.0.2” denotes the gateway and also specifies that it is reachable through router1's Serial 1 interface. Router3's routing table displays similar entries Rotuer3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 1.0.0.0/8 [120/1] via 11.0.0.1, 00:00:00, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 C 11.0.0.0/8 is directly connected, Serial0 To view more details regarding the configured Routing Protocol (RIP in our case), let's use the “show ip protocols” command.

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This will display routing protocol details along with certain parameters like timers, default AD value, routed networks, RIP version etc Router3#sh ip protocols Routing Protocol is "rip" Sending updates every 30 seconds, next due in 2 seconds Invalid after 180 seconds, hold down 180, flushed after 240 Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Redistributing: rip Default version control: send version 1, receive any version Interface Send Recv Triggered RIP Key-chain Loopback0 1 1 2 Serial0 1 1 2 Automatic network summarization is in effect Routing for Networks: 3.0.0.0 11.0.0.0 Routing Information Sources: Gateway Distance Last Update 11.0.0.1 120 00:00:17 Distance: (default is 120) Router1#sh ip protocols Routing Protocol is "rip" Sending updates every 30 seconds, next due in 24 seconds Invalid after 180 seconds, hold down 180, flushed after 240 (Displays various timer values) Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Redistributing: rip Default version control: send version 1, receive any version (Configured RIP Version is 1) Interface Send Recv Triggered RIP Key-chain Loopback0 1 1 2 Serial1 1 1 2 Automatic network summarization is in effect Routing for Networks: (Displays networks published) 1.0.0.0 11.0.0.0 Routing Information Sources: Gateway Distance Last Update 11.0.0.2 120 00:00:16 Distance: (default is 120) (Displays default AD value) To view what information is exchanged between routers running RIP, let's debug the RIP's operation using debug ip rip command Rotuer3#debug ip rip RIP protocol debugging is on Rotuer3# 01:05:49: RIP: received v1 update from 11.0.0.1 on Serial0

(V1 represents version 1) 01:05:49: 1.0.0.0 in 1 hops (This is what is received from router1) 01:05:59: RIP: sending v1 update to 255.255.255.255 via Loopback0 (3.3.3.3)

(Broadcast update sent) 01:05:59: RIP: build update entries

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01:05:59: network 1.0.0.0 metric 2 (metric refers to hop count) 01:05:59: network 11.0.0.0 metric 1 01:05:59: RIP: sending v1 update to 255.255.255.255 via Serial0 (11.0.0.2) 01:05:59: RIP: build update entries 01:05:59: network 3.0.0.0 metric 1 01:06:18: RIP: received v1 update from 11.0.0.1 on Serial0

(30 sec periodic update) 01:06:18: 1.0.0.0 in 1 hops 01:06:27: RIP: sending v1 update to 255.255.255.255 via Loopback0 (3.3.3.3) 01:06:27: RIP: build update entries 01:06:27: network 1.0.0.0 metric 2 01:06:27: network 11.0.0.0 metric 1 01:06:27: RIP: sending v1 update to 255.255.255.255 via Serial0 (11.0.0.2) 01:06:27: RIP: build update entries 01:06:27: network 3.0.0.0 metric 1 Rotuer3#undebug all (to switch off all debugging) Observe that full routing table is not sent as updates in all directions – because of split horizon rule. Let’s see how similar the debug output is in router1 Router1#debug ip rip RIP protocol debugging is on Router1# 01:07:50: RIP: received v1 update from 11.0.0.2 on Serial1 01:07:50: 3.0.0.0 in 1 hops 01:08:05: RIP: sending v1 update to 255.255.255.255 via Loopback0 (1.1.1.1) 01:08:05: RIP: build update entries 01:08:05: network 3.0.0.0 metric 2 01:08:05: network 11.0.0.0 metric 1 01:08:05: RIP: sending v1 update to 255.255.255.255 via Serial1 (11.0.0.1) 01:08:05: RIP: build update entries 01:08:05: network 1.0.0.0 metric 1 01:08:18: RIP: received v1 update from 11.0.0.2 on Serial1 01:08:18: 3.0.0.0 in 1 hops 01:08:33: RIP: sending v1 update to 255.255.255.255 via Loopback0 (1.1.1.1) 01:08:33: RIP: build update entries 01:08:33: network 3.0.0.0 metric 2 01:08:33: network 11.0.0.0 metric 1 01:08:33: RIP: sending v1 update to 255.255.255.255 via Serial1 (11.0.0.1) 01:08:33: RIP: build update entries 01:08:33: network 1.0.0.0 metric 1 Rotuer1#undebug all To verify the dynamic nature of the routing protocol, let's emulate a network going down by shutting down the loopback 0 of router1 & observe the debug output

Router1(config)#int loopback 0 Router1(config-if)#shut

X Router1 Router3

3.3.3.3 L 0 L 0

1.1.1.1

Serial 1 Serial 0

11.0.0.2 11.0.0.1

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Router1(config-if)# 01:21:17: %LINK-5-CHANGED: Interface Loopback0, changed state to administratively down Router1#debug ip rip RIP protocol debugging is on 01:21:17: RIP: sending v1 flash update to 255.255.255.255 via Serial1 (11.0.0.1) (this indicates a Triggered Update) 01:21:17: RIP: build flash update entries 01:21:17: network 1.0.0.0 metric 16 (metric 16 means infinity for RIP – route poisoning) 01:21:19: RIP: received v1 update from 11.0.0.2 on Serial1 01:21:19: 1.0.0.0 in 16 hops (inaccessible) (“inaccessible” implies that Poison-Reverse message is received from Router3) 01:21:22: RIP: sending v1 update to 255.255.255.255 via Serial1 (11.0.0.1) 01:21:22: RIP: build update entries 01:21:22: network 1.0.0.0 metric 16 Router1(config-if)#^Z Now this change is also reflected in the routing table – a network that’s gone down is immediately removed from the routing table. Router1#sh ip route 01:21:30: %SYS-5-CONFIG_I: Configured from console by consoleroute Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set R 3.0.0.0/8 [120/1] via 11.0.0.2, 00:00:22, Serial1 C 11.0.0.0/8 is directly connected, Serial1 The above experiment reveals that the routers exchange network connectivity information

(i) During Startup (ii) Periodically (once in 30 secs) (iii) Triggered (whenever network changes occur)

We are also able to observe how split horizon functions to ensure routing updates are not sent in the direction from where they were learnt. Route poisoning & poison reverse were also observed.

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IGRP In this scenario, let’s complete the basic interface configurations, check the routing table content without configuring the routing protocol & then proceed with protocol configuration & verification. A partial running-config output reveals interface configuration Router1#sh run Building configuration... <output omitted> ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial1 ip address 100.0.0.1 255.0.0.0 <output omitted> ! End The routing table reveals that the connected networks are up Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 100.0.0.0/8 is directly connected, Serial1 Let’s now configure IGRP routing protocol using “router igrp <AS number>” command & publish connected networks using “network <network id>” command. Router1(config)#router igrp 100 (100 is the Autonomous System) Router1(config-router)#network 1.0.0.0

Router1 Router3

L 0 L 0 3.3.3.3 1.1.1.1

Serial 1 Serial 0

100.0.0.22

100.0.0.111

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Router1(config-router)#network 100.0.0.0 (publish directly connected networks)

The running config on routers 1 & 3 now display the protocol configuration too. Router1#sh run Building configuration... <output omitted> ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial1 ip address 100.0.0.1 255.0.0.0 ! router igrp 100 network 1.0.0.0 network 100.0.0.0 ! <output omitted> ! End Router3(Config)#router igrp 100 (This AS number must be similar on all the routers) Router3(Config-router)# network 3.0.0.0 Router3(Config-router)# network 100.0.0.0 Router3#sh run Building configuration... Current configuration : 776 bytes ! <output omitted> ! interface Loopback0 ip address 3.3.3.3 255.0.0.0 ! interface Serial0 ip address 100.0.0.2 255.0.0.0 clockrate 64000 ! router igrp 100 network 3.0.0.0 network 100.0.0.0 ! <output omitted> ! end After configuring IGRP let’s see if the routing tables of Routers 1 & 3 have information about IGRP learnt routes. Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B –

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BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 100.0.0.0/8 is directly connected, Serial1 I 3.0.0.0/8 [100/8976] via 100.0.0.2, 00:00:01, Serial1 Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set I 1.0.0.0/8 [100/8976] via 100.0.0.1, 00:01:03, Serial0 C 100.0.0.0/8 is directly connected, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 The I implies that this is an IGRP learnt route. 100 stands for the AD value & 8976 is the metric (composite – BW & Delay) “sh ip protocols” command gives us other useful information – same as what we saw for RIP. Router1#sh ip protocols Routing Protocol is "igrp 100" Sending updates every 90 seconds, next due in 37 seconds Invalid after 270 seconds, hold down 280, flushed after 630 Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Default networks flagged in outgoing updates Default networks accepted from incoming updates IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 IGRP maximum hopcount 100 IGRP maximum metric variance 1 Redistributing: igrp 100 Routing for Networks: 1.0.0.0 100.0.0.0 Routing Information Sources: Gateway Distance Last Update 100.0.0.2 100 00:00:09 Distance: (default is 100) Router3#sh ip protocols Routing Protocol is "igrp 100"

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Sending updates every 90 seconds, next due in 17 seconds Invalid after 270 seconds, hold down 280, flushed after 630 Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is Default networks flagged in outgoing updates Default networks accepted from incoming updates IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 IGRP maximum hopcount 100 IGRP maximum metric variance 1 Redistributing: igrp 100 Routing for Networks: 3.0.0.0 100.0.0.0 Routing Information Sources: Gateway Distance Last Update 100.0.0.1 100 00:00:13 Distance: (default is 100) “Debug ip igrp transactions” command give us details reg the metric, updates etc Rotuer3#debug ip igrp transactions IGRP protocol debugging is on Rotuer3# 00:29:14:IGRP: received update from 100.0.0.1 on Serial0 00:29:14: network 1.0.0.0, metric 8976 (neighbor 501) 00:29:19:IGRP: sending update to 255.255.255.255 via Loopback0 (3.3.3.3) 00:29:19: network 1.0.0.0, metric=8976 00:29:19: network 100.0.0.0, metric=8476 00:29:19:IGRP: sending update to 255.255.255.255 via Serial0 (100.0.0.2) 00:29:19: network 3.0.0.0, metric=501 00:30:32:IGRP: sending update to 255.255.255.255 via Loopback0 (3.3.3.3) 00:30:32: network 1.0.0.0, metric=8976 00:30:32: network 100.0.0.0, metric=8476 00:30:32:IGRP: sending update to 255.255.255.255 via Serial0 (100.0.0.2) 00:30:32: network 3.0.0.0, metric=501 00:30:38:IGRP: received update from 100.0.0.1 on Serial0 00:30:38: network 1.0.0.0, metric 8976 (neighbor 501) Let’s simulate a problem of network going down - on Router1. We’ll shutdown the loopback 0 interface and this should reflect in router3’s Routing Table – will display possibly down message for the hold-down time period (280 secs).

Router1(config)#int loopback 0 Router1(config-if)#shutdown

X Router1 Router3

3.3.3.3 L 0 L 0

1.1.1.1

Serial 1 Serial 0

100.0.0.2 100.0.0.1

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Router1#sh run Building configuration... Current configuration : 693 bytes ! hostname Router1 ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 Shutdown Observe the debug output after shutting down the loopback 0 interface of router1 the metric value for network 1.0.0.0 goes to 4294967295 – representing infinity. Router3#debug ip igrp transactions IGRP protocol debugging is on 00:47:00: IGRP: received update from 100.0.0.1 on Serial0 00:47:00: network 1.0.0.0, metric 4294967295 (inaccessible) 00:47:00: IGRP: edition is now 3 00:47:00: IGRP: sending update to 255.255.255.255 via Loopback0 (3.3.3.3) The routing table now reflects this change as “possibly down” – doesn’t remove the entry immediately – waits for hold-down timer to expire and then decides to remove the entry/reinstate the entry if the network has come up! Rotuer3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route Gateway of last resort is not set I 1.0.0.0/8 is possibly down, routing via 100.0.0.1, Serial0 C 100.0.0.0/8 is directly connected, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 Note : If the entry were to be removed, it’s not done so immediately after hold down timer expires. It’s removed only after the flush timer (630 secs) expires.

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S0

S1 S1

1.1.1.1 3.3.3.3 25.0.0.1 25.0.0.2

50.0.0.2 50.0.0.1

S0

L0 L0 Router3 Router1

EIGRP

BASIC CONFIGURATION In this case, we’ll consider a slightly different scenario where we have two paths to a destination. We’ll be able to understand redundancy & load balancing also with this case study. Let’s first configure the Routers according to the above diagram & observe the routing table without configuring the routing protocols. Router1(config)# Router1(config)#int loop 0 Router1(config-if)#ip add 1.1.1.1 255.0.0.0 Router1(config-if)#exit Router1(config)#int s0 Router1(config-if)#ip add 25.0.0.1 255.0.0.0 Router1(config-if)#no shut Router1(config-if)#exit Router1(config)#int s1 Router1(config-if)#ip add 50.0.0.1 255.0.0.0 Router1(config-if)#no shut Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 50.0.0.0/8 is directly connected, Serial1 C 25.0.0.0/8 is directly connected, Serial0 Similarly Configure Router3 & check out it’s Routing Table Router3(config)#int loop 0 Router3(config-if)#ip add 3.3.3.3 255.0.0.0 Router3(config-if)#exit Router3(config)#int s0 Router3(config-if)#ip add 25.0.0.2 255.0.0.0 Router3(config-if)#clock rate 64000 Router3(config-if)#no shut

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Router3(config-if)#exit Router3(config)#int s1 Router3(config-if)#ip add 50.0.0.2 255.0.0.0 Router3(config-if)#clock rate 64000 Router3(config-if)#no shut Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 50.0.0.0/8 is directly connected, Serial1 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial0 I)EIGRP OPERATION WITH EQUAL COST LOAD BALANCING ENABLING EIGRP Now, we’ll enable the routing protocol on both the routers using “Router EIGRP <AS number>” command & publish Networks using “Network <Network id>” command Router1(config)#router eigrp 200 Router1(config-router)#net 1.0.0.0 Router1(config-router)#net 25.0.0.0 Router1(config-router)#net 50.0.0.0 Router3(config)#router eigrp 200 Router3(config-router)#net 3.0.0.0 Router3(config-router)#net 25.0.0.0 Router3(config-router)#net 50.0.0.0 Let’s see how this configuration reflects in the running configuration of Router1 & Router3 Router1#sh run Building configuration... <output omitted> interface Serial0 ip address 25.0.0.1 255.0.0.0 ! interface Serial1 ip address 50.0.0.1 255.0.0.0 ! router eigrp 200 network 1.0.0.0 network 25.0.0.0 network 50.0.0.0 auto-summary (Observe this is automatically added!)

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no eigrp log-neighbor-changes ! <output omitted> End Router3#sh run Building configuration... <output omitted> interface Serial0 ip address 25.0.0.2 255.0.0.0 clockrate 64000 ! interface Serial1 ip address 50.0.0.2 255.0.0.0 clockrate 64000 ! router eigrp 200 network 3.0.0.0 network 25.0.0.0 network 50.0.0.0 auto-summary (Automatically added indicating Auto-summarisation) no eigrp log-neighbor-changes) <output omitted> End THE ROUTING TABLE As there are 2 equally good paths between the routers, 2 routes must be seen in the routing table of these routers. We can also see “D” in the first column of the highlighted entry indicating EIGRP learnt routes. Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 50.0.0.0/8 is directly connected, Serial1 D 3.0.0.0/8 [90/2297856] via 25.0.0.2, 00:02:25, Serial0 [90/2297856] via 50.0.0.2, 00:02:25, Serial1 C 25.0.0.0/8 is directly connected, Serial0 The above indicates two paths to reach network 3.0.0.0 from Router1. A similar table can be seen in Router3. Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E –

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EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set D 1.0.0.0/8 [90/2297856] via 25.0.0.1, 00:03:08, Serial0 [90/2297856] via 50.0.0.1, 00:03:08, Serial1 C 50.0.0.0/8 is directly connected, Serial1 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial0 The “show ip route eigrp” command displays only EIGRP learnt routes. Router1#sh ip route eigrp D 3.0.0.0/8 [90/2297856] via 25.0.0.2, 00:04:43, Serial0

[90/2297856] via 25.0.0.2, 00:04:43, Serial0 Router3#sh ip route eigrp D 1.0.0.0/8 [90/2297856] via 25.0.0.1, 00:03:19, Serial0 [90/2297856] via 50.0.0.1, 00:03:19, Serial1 THE NEIGHBOR TABLE Let’s look at the neighbor table contents next. We use the “sh ip eigrp neighbors” command. In this case, the same neighbor is learnt via 2 paths & hence 2 entries. Had there been only one path between the 2 routers, only one entry would be seen. Router1#sh ip eigrp neighbors IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 1 50.0.0.2 Se1 14 00:01:47 28 200 0 6 0 25.0.0.2 Se0 14 00:09:34 30 200 0 5 The first column indicates the order of learning Neighbors. The next column points the connected interface IP of the neighbor. Third column is this router’s interface through which the neighbor is connected. A similar table is seen on Router3 as well. Router3#sh ip eigrp neighbors IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 1 50.0.0.1 Se1 11 00:03:32 28 200 0 6 0 25.0.0.1 Se0 11 00:11:12 726 4356 0 7

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THE TOPOLOGY TABLE Let’s now view the topology table entries using the “sh ip eigrp topology” command. We should be able to see the “successor” & “feasible successor” apart from Feasible & Advertised Distance values. Router1#sh ip eigrp topology IP-EIGRP Topology Table for AS(200)/ID(1.1.1.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 1.0.0.0/8, 1 successors, FD is 128256 via Connected, Loopback0 via Summary (128256/0), Null0 P 3.0.0.0/8, 2 successors, FD is 2297856 via 50.0.0.2 (2297856/128256), Serial1 (Both are equally good) via 25.0.0.2 (2297856/128256), Serial0 (Hence two successors ) P 25.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial0 via Summary (2169856/0), Null0 P 50.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial1 via Summary (2169856/0), Null0 In the highlighted entry “(2297856/128256)” 2297856 is the feasible distance & 128256 is the advertised distance. If both paths were with different metrics, the one with the best metric would have been the successor & the other feasible successor. Then it would display 1 successor & not 2 successors as we’ll see in the next section. “P”in the first column indicates that it’s in the passive state. Let’s observe Router3’s Topology Table – much the same ! Router3#sh ip eigrp topology IP-EIGRP Topology Table for AS(200)/ID(3.3.3.3) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 1.0.0.0/8, 2 successors, FD is 2297856 via 50.0.0.1 (2297856/128256), Serial1 via 25.0.0.1 (2297856/128256), Serial0 P 3.0.0.0/8, 1 successors, FD is 128256 via Connected, Loopback0 via Summary (128256/0), Null0 P 25.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial0 via Summary (2169856/0), Null0 P 50.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial1 via Summary (2169856/0), Null0

58

S0

S1 S1

1.1.1.1 3.3.3.3 25.0.0.1 25.0.0.2

50.0.0.2 50.0.0.1

S0

L0 L0 Router3 Router1

II) EIGRP REDUNDANCY – BACKUP PATH

We’ll change the bandwidth of both the paths ensuring they have different metrics. Router1#conf t Router1(config)#int s1 Router1(config-if)#bandwidth 128 Another useful command to view the running config of a specific interface is “sh run interface <type id>” Router1#sh run int s1 Building configuration... Current configuration : 88 bytes ! interface Serial1 bandwidth 128 ip address 50.0.0.2 255.0.0.0 end Let’s change on Router3 also Router3#conf t Router3(config)#int s1 Router3(config-if)#bandwidth 128 Router3#sh run int s1 Building configuration... Current configuration : 88 bytes ! interface Serial1 bandwidth 128 ip address 50.0.0.2 255.0.0.0 clockrate 64000 end Having changed the metrics, we now have one path which is better than the other. So we’ll be able to see only the best path in the Routing table. Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-

59

IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 50.0.0.0/8 is directly connected, Serial1 D 3.0.0.0/8 [90/2297856] via 25.0.0.2, 00:01:36, Serial0 C 25.0.0.0/8 is directly connected, Serial0 If we see the topology table, we’ll be able to see both – the best (successor) & the next best (feasible successor) paths Router1#sh ip eigrp topology IP-EIGRP Topology Table for AS(200)/ID(1.1.1.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 1.0.0.0/8, 1 successors, FD is 128256 via Connected, Loopback0 via Summary (128256/0), Null0 P 3.0.0.0/8, 1 successors, FD is 2297856 (1 successor is displayed) via 25.0.0.2 (2297856/128256), Serial0 (Successor) via 50.0.0.2 (20640000/128256), Serial1 (Feasible Successor) P 25.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial0 via Summary (2169856/0), Null0 P 50.0.0.0/8, 1 successors, FD is 20512000 via Connected, Serial1 via Summary (20512000/0), Null0 However, the neighbor table is still the same. Router1#sh ip eigrp nei IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 0 25.0.0.2 Se0 10 00:00:44 32 200 0 25 1 50.0.0.2 Se1 14 00:25:33 36 1140 0 24 Let’s see the tables of Router3 Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set D 1.0.0.0/8 [90/2297856] via 25.0.0.1, 00:00:40, Serial0 C 50.0.0.0/8 is directly connected, Serial1

60

S0

S1 S1

1.1.1.1 3.3.3.3 25.0.0.1 25.0.0.2

50.0.0.2 50.0.0.1

S0

L0 L0 Router3 Router1

X

C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial0 Router3#sh ip eigrp topology IP-EIGRP Topology Table for AS(200)/ID(3.3.3.3) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 1.0.0.0/8, 1 successors, FD is 2297856 via 25.0.0.1 (2297856/128256), Serial0 via 50.0.0.1 (20640000/128256), Serial1 P 3.0.0.0/8, 1 successors, FD is 128256 via Connected, Loopback0 via Summary (128256/0), Null0 P 25.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial0 via Summary (2169856/0), Null0 P 50.0.0.0/8, 1 successors, FD is 2169856 via Connected, Serial1 via Summary (20512000/0), Null0 Router3#sh ip eigrp neighbors IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 0 25.0.0.1 Se0 13 00:01:56 29 200 0 23 1 50.0.0.1 Se1 10 00:26:51 38 1140 0 22

Back up path If the best path goes down, the feasible successor immediately gets installed in the routing table. This is how the feasible successor works like a backup path. To simulate this situation, let’s bring down Router1’s Serial 0.

Router1#conf t Router1(config)#int s0 Router1(config-if)#shutdown Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-

61

S0

S1 S1

1.1.1.1 3.3.3.3 25.0.0.1 25.0.0.2

50.0.0.2 50.0.0.1

S0

L0 L0 Router3 Router1

IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 50.0.0.0/8 is directly connected, Serial1 D 3.0.0.0/8 [90/20640000] via 50.0.0.2, 00:00:23, Serial1 The second path (feasible successor) is automatically installed in the Routing table. Even the neighbor table displays only one entry, indicating that only this link is up and the other is down. Router1#sh ip eigrp nei IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 1 50.0.0.2 Se1 10 00:15:46 53 1140 0 15 Similar changes can be observed on Router3’s tables as well. Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set D 1.0.0.0/8 [90/20640000] via 50.0.0.1, 00:01:03, Serial1 C 50.0.0.0/8 is directly connected, Serial1 C 3.0.0.0/8 is directly connected, Loopback0 Router3#sh ip eigrp nei IP-EIGRP neighbors for process 200 H Address Interface Hold Uptime SRTT RTO Q Seq Type (sec) (ms) Cnt Num 1 50.0.0.1 Se1 14 00:12:23 45 1140 0 15 III) UNEQUAL COST LOAD BALANCING

If we want to ensure both the paths carry the traffic proportionately (load balance), it’s possible for us to “instruct” IGRP & EIGRP to do so using the “variance <value>” command.

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In the above case, the ratio between the successor metric & the feasible successor metric is 20640000 /2297856 = 8.98. Round it to 9. If we choose a variance of 9, it means that all paths within this ratio (w.r.t successor) would be considered for load balancing (max 6 paths). Hence we’ll be able to see the second entry in the Routing Table even though its metric is not the best. Shall we check it out? To do so, we must configure variance on Router1 & Router3. Router1(config)#router eigrp 200 Router1(config-router)#variance 10 Router3(config)#router eigrp 200 Router3(config-router)#variance 10 Let’s see how it reflects in the routing table. Router1#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 C 50.0.0.0/8 is directly connected, Serial1 D 3.0.0.0/8 [90/2297856] via 25.0.0.2, 00:00:01, Serial0 [90/20640000] via 50.0.0.2, 00:00:01, Serial1 C 25.0.0.0/8 is directly connected, Serial0 Router3#show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set D 1.0.0.0/8 [90/2297856] via 25.0.0.1, 00:00:03, Serial0 [90/20640000] via 50.0.0.1, 00:00:03, Serial1 C 50.0.0.0/8 is directly connected, Serial1 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial0 This clearly tells us that traffic is carried proportionately on both the paths.

63

OSPF

I) OSPF ON POINT-TO-POINT WAN LINK OSPF offers the widest features & its behavior is different in different environments. The first case we‟ll take up is point to point WAN and understand OSPF operation. Consider the below diagram.

IP ADDRESS CONFIGURATION Router1(config)#int loopback 0 Router1(config-if)#ip add 1.1.1.1 255.0.0.0 Router1(config-if)#exit Router1(config)#int serial 0 Router1(config-if)#ip add 25.0.0.1 255.0.0.0 Router1(config-if)#no shut Router1(config-if)#exit Router3(config)#int loopback 0 Router3(config-if)#ip add 3.3.3.3 255.0.0.0 Router3(config-if)#exit Router3(config)#int serial0 Router3(config-if)#ip add 25.0.0.2 255.0.0.0 Router3(config-if)#clock rate 64000 Router3(config-if)#no shut Router3(config-if)#exit OSPF CONFIGURATION To configure the OSPF Routing Protocol, we use “router OSPF <process id> syntax. A point to be noted is that the process id can be different in different routers – this does not refer to the Autonomous System number like other protocols. The command to publish Networks is “network <net id><wild card mask><area><area id>” Router1(config)#router ospf 1 Router1(config-router)#network 1.0.0.0 0.255.255.255 area 0 Router1(config-router)#network 25.0.0.0 0.255.255.255 area 0 Router3(config)#router ospf 3 Router3(config-router)#network 3.0.0.0 0.255.255.255 area 0 Router3(config-router)#network 25.0.0.0 0.255.255.255 area 0

L0 L0 S0 S0 Router 1 Router 3

1.1.1.1 3.3.3.3 25.0.0.1 25.0.0.2

64

VERIFICATION Let’s verify OSPF configuration & operation just like we did with other protocols. Router1#sh run Building configuration... Current configuration : 773 bytes ! hostname Router1 ! enable password cisco ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial0 ip address 25.0.0.1 255.0.0.0 ! router ospf 1 log-adjacency-changes network 1.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! End Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/65] via 25.0.0.2, 00:04:41, Serial0 C 25.0.0.0/8 is directly connected, Serial0 Router1#sh ip route ospf 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/65] via 25.0.0.2, 00:04:47, Serial0 Router1#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 FULL/ - 00:00:33 25.0.0.2 Serial0

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A new command is “sh ip ospf interface”. The highlighted part in the output gives us some important information. Router1#sh ip ospf interface Serial0 is up, line protocol is up Internet Address 25.0.0.1/8, Area 0 Process ID 1, Router ID 1.1.1.1,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:05 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 3.3.3.3 Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 1.1.1.1/8, Area 0 Process ID 1, Router ID 1.1.1.1, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host The database table will give us information about various types of link state advertisements. In this example, we see only “router link states” within a single area – area 0 Each router in the area advertises details of links connected to it. This advertisement is seen only within the area to which the router is connected. “Link id” represents the advertising router’s router id – “ADV Router” also refers to the same info. “Link count” represents the no. of links connected to this router within this area. Router1#sh ip ospf database OSPF Router with ID (1.1.1.1) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 158 0x80000003 0x9BAA 3 3.3.3.3 3.3.3.3 159 0x80000003 0xD163 3 We’ll be able to make similar observations on Router3 also. Router3#sh run Building configuration... Current configuration : 837 bytes ! hostname Router3 ! enable password cisco ! interface Loopback0 ip address 3.3.3.3 255.0.0.0

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! interface Serial0 ip address 25.0.0.2 255.0.0.0 clockrate 64000 ! router ospf 3 log-adjacency-changes network 3.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/65] via 25.0.0.1, 00:05:26, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial0 Router3#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/65] via 25.0.0.1, 00:05:29, Serial0 Router3#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL/ - 00:00:39 25.0.0.1 Serial0 Network type is shown as POINT_TO_POINT for a WAN link Router3#sh ip ospf interface Serial0 is up, line protocol is up Internet Address 25.0.0.2/8, Area 0 Process ID 3, Router ID 3.3.3.3,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:02 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0)

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Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 1.1.1.1 Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 3.3.3.3/8, Area 0 Process ID 3, Router ID 3.3.3.3, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host Router3#sh ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 3) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 362 0x80000003 0x9BAA 3 3.3.3.3 3.3.3.3 362 0x80000003 0xD163 3

II) OSPF IN LAN :

We’ll be able to observe the election of DR & BDR. We’ll see additional entries in database table. CONFIGURATION Router1(config)#int loop 0 Router1(config-if)#ip add 1.1.1.1 255.0.0.0 Router1(config-if)#exit Router1(config)#int e0 Router1(config-if)#ip add 25.0.0.1 255.0.0.0 Router1(config-if)#no shut Router1(config-if)#exit Router1(config)#router ospf 1 Router1(config-router)#network 1.0.0.0 0.255.255.255 area 0 Router1(config-router)#network 25.0.0.0 0.255.255.255 area 0 Router2(config)#int loop 0

L0 L0

L0

F0/0

E0 Router 1 Router 3

Router 2

1.1.1.1

2.2.2.2

3.3.3.3 25.0.0.1

25.0.0.2

25.0.0.3 E0

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Router2(config-if)#ip add 2.2.2.2 255.0.0.0 Router2(config-if)#exit Router2(config)#int f0/0 Router2(config-if)#ip add 25.0.0.2 255.0.0.0 Router2(config-if)#no shut Router2(config-if)#exit Router2(config)#router ospf 2 Router2(config-router)#network 2.0.0.0 0.255.255.255 area 0 Router2(config-router)#network 25.0.0.0 0.255.255.255 area 0 Router3(config)#int loop 0 Router3(config-if)#ip add 3.3.3.3 255.0.0.0 Router3(config-if)#exit Router3(config)#int e0 Router3(config-if)#ip add 25.0.0.3 255.0.0.0 Router3(config-if)#no shut Router3(config-if)#exit Router3(config)#router ospf 3 Router3(config-router)#network 3.0.0.0 0.255.255.255 area 0 Router3(config-router)#network 25.0.0.0 0.255.255.255 area 0 Router1# sh run Building configuration... Current configuration : 773 bytes ! hostname Router1 ! enable password cisco ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Ethernet0 ip address 25.0.0.1 255.0.0.0 ! router ospf 1 log-adjacency-changes network 1.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! End Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E –

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EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/11] via 25.0.0.2, 00:25:03, Ethernet0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/11] via 25.0.0.3, 00:25:03, Ethernet0 C 25.0.0.0/8 is directly connected, Ethernet0 Router1#sh ip route ospf 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/11] via 25.0.0.2, 00:25:07, Ethernet0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/11] via 25.0.0.3, 00:25:07, Ethernet0 The neighbor table “state” tells us the state of each neighbor router in the lan – DR/BDR/DROTHER Router1#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 FULL/DROTHER 00:00:38 25.0.0.3 Ethernet0 2.2.2.2 1 FULL/BDR 00:00:35 25.0.0.2 Ethernet0 In the below output, observe - Network type is shown as Broadcast. Router1#sh ip ospf interface Ethernet0 is up, line protocol is up Internet Address 25.0.0.1/8, Area 0 Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 1.1.1.1, Interface address 25.0.0.1 Backup Designated router (ID) 2.2.2.2, Interface address 25.0.0.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:09 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 2 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 3.3.3.3 Adjacent with neighbor 2.2.2.2 (Backup Designated Router) Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 1.1.1.1/8, Area 0 Process ID 1, Router ID 1.1.1.1, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host An additional entry – “Net Link State” – displays the advertisement by a DR in LAN. There would be as many entries as there are LANs in this area. Router1#sh ip ospf database

70

OSPF Router with ID (1.1.1.1) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 1552 0x80000002 0xFBDB 2 2.2.2.2 2.2.2.2 1553 0x80000003 0xEBB 2 3.3.3.3 3.3.3.3 1542 0x80000002 0x2499 2 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 25.0.0.1 1.1.1.1 1542 0x80000002 0x748A Link Id represents the Ethernet interface address of Router1 & Adv. Router represents the Router id of Router1. NOTE : Router id is the highest loopback address. If there is no loopback defined, then it’s the highest active interface address. Similar details can be seen on Router2 & Router3 as below. Router2#sh ru Building configuration... Current configuration : 803 bytes ! hostname "Router2" ! enable password cisco ! interface Loopback0 ip address 2.2.2.2 255.0.0.0 ! interface FastEthernet0/0 ip address 25.0.0.2 255.0.0.0 duplex auto speed auto ! router ospf 2 log-adjacency-changes network 2.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 line aux 0 line vty 0 4 password cisco login ! end Router2#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E –

71

EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/11] via 25.0.0.1, 00:27:37, FastEthernet0/0 C 2.0.0.0/8 is directly connected, Loopback0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/11] via 25.0.0.3, 00:27:37, FastEthernet0/0 C 25.0.0.0/8 is directly connected, FastEthernet0/0 Router2#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/11] via 25.0.0.1, 00:27:44, FastEthernet0/0 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/11] via 25.0.0.3, 00:27:44, FastEthernet0/0 Router2#sh ip ospf interface FastEthernet0/0 is up, line protocol is up Internet Address 25.0.0.2/8, Area 0 Process ID 2, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 1.1.1.1, Interface address 25.0.0.1 Backup Designated router (ID) 2.2.2.2, Interface address 25.0.0.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:04 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 3.3.3.3 Adjacent with neighbor 1.1.1.1 (Designated Router) Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 2.2.2.2/8, Area 0 Process ID 2, Router ID 2.2.2.2, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host Router2#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 FULL/DROTHER 00:00:37 25.0.0.3 FastEthernet0/0 1.1.1.1 1 FULL/DR 00:00:35 25.0.0.1 FastEthernet0/0 Observe that the Router database tables of all the routers within the same area have the same details under ROUTER LINK STATES. Router2#sh ip ospf database OSPF Router with ID (2.2.2.2) (Process ID 2) Router Link States (Area 0)

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Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 1705 0x80000002 0x00FBDB 2 2.2.2.2 2.2.2.2 1705 0x80000003 0x000EBB 2 3.3.3.3 3.3.3.3 1695 0x80000002 0x002499 2 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 25.0.0.1 1.1.1.1 1696 0x80000002 0x00748A Router3#sh run Building configuration... Current configuration : 820 bytes ! hostname Router3 ! enable password cisco ! interface Loopback0 ip address 3.3.3.3 255.0.0.0 ! interface Ethernet0 ip address 25.0.0.3 255.0.0.0 ! router ospf 3 log-adjacency-changes network 3.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/11] via 25.0.0.1, 00:30:16, Ethernet0 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/11] via 25.0.0.2, 00:30:16, Ethernet0 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Ethernet0

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Router3#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O 1.1.1.1 [110/11] via 25.0.0.1, 00:30:21, Ethernet0 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/11] via 25.0.0.2, 00:30:21, Ethernet0 Router3#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 2.2.2.2 1 FULL/BDR 00:00:31 25.0.0.2 Ethernet0 1.1.1.1 1 FULL/DR 00:00:31 25.0.0.1 Ethernet0 Router3#sh ip ospf interface Ethernet0 is up, line protocol is up Internet Address 25.0.0.3/8, Area 0 Process ID 3, Router ID 3.3.3.3, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DROTHER, Priority 1 Designated Router (ID) 1.1.1.1, Interface address 25.0.0.1 Backup Designated router (ID) 2.2.2.2, Interface address 25.0.0.2 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:07 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 0, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 2, Adjacent neighbor count is 2 Adjacent with neighbor 2.2.2.2 (Backup Designated Router) Adjacent with neighbor 1.1.1.1 (Designated Router) Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 3.3.3.3/8, Area 0 Process ID 3, Router ID 3.3.3.3, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host Router3#sh ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 3) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 37 0x80000003 0xF9DC 2 2.2.2.2 2.2.2.2 1866 0x80000003 0xEBB 2 3.3.3.3 3.3.3.3 1856 0x80000002 0x2499 2 Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 25.0.0.1 1.1.1.1 38 0x80000003 0x728B OSPF MULTI AREA We’ll configure 3 routers in a multi-area environment comprising area 0, 1 & 2. The configuration & database table differences can be seen in the relevant outputs.

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CONFIGURATION : Router1(config)#int loop 0 Router1(config-if)#ip add 1.1.1.1 255.0.0.0 Router1(config-if)#exit Router1(config)#int s1 Router1(config-if)#ip add 25.0.0.1 255.0.0.0 Router1(config-if)#no shut Router1(config-if)#exit Router1(config)#router ospf 1 Router1(config-router)#network 1.0.0.0 0.255.255.255 area 1 Router1(config-router)#network 25.0.0.0 0.255.255.255 area 0 (Note that the area ids differ in the above syntax) Router1#sh run Building configuration... Current configuration : 773 bytes ! hostname Router1 ! enable password cisco ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial1 ip address 25.0.0.1 255.0.0.0 ! router ospf 1 log-adjacency-changes network 1.0.0.0 0.255.255.255 area 1 network 25.0.0.0 0.255.255.255 area 0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router2#sh run Building configuration...

L0

L0

L0 S0/0

S0 S1 S1 50.0.0.1

Router 1 Router 1 Router 3 Router 2

1.1.1.1 3.3.3.3

25.0.0.1 25.0.0.2 50.0.0.2

Area 0 Area1 Area 2

2.2.2.2

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Current configuration : 803 bytes ! hostname "Router2" ! enable password cisco ! interface Loopback0 ip address 2.2.2.2 255.0.0.0 ! interface Serial0/0 ip address 50.0.0.2 255.0.0.0 no fair-queue ! router ospf 2 log-adjacency-changes network 2.0.0.0 0.255.255.255 area 2 network 50.0.0.0 0.255.255.255 area 2 ! line con 0 line aux 0 line vty 0 4 password cisco login ! end Router3#sh run Building configuration... Current configuration : 899 bytes ! enable password cisco ! interface Loopback0 ip address 3.3.3.3 255.0.0.0 ! interface Serial0 ip address 50.0.0.1 255.0.0.0 clockrate 64000 ! interface Serial1 ip address 25.0.0.2 255.0.0.0 clockrate 64000 ! router ospf 3 log-adjacency-changes network 3.0.0.0 0.255.255.255 area 0 network 25.0.0.0 0.255.255.255 area 0 network 50.0.0.0 0.255.255.255 area 2 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end

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ROUTING TABLE : Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 O IA 50.0.0.0/8 [110/192] via 25.0.0.2, 00:03:44, Serial1 2.0.0.0/32 is subnetted, 1 subnets O IA 2.2.2.2 [110/129] via 25.0.0.2, 00:03:44, Serial1 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/65] via 25.0.0.2, 00:03:44, Serial1 C 25.0.0.0/8 is directly connected, Serial1 In the above output, “O” represents OSPF learnt routes within the same area & “O IA” represents inter-area learnt OSPF routes. Router1#sh ip route ospf O IA 50.0.0.0/8 [110/192] via 25.0.0.2, 00:03:51, Serial1 2.0.0.0/32 is subnetted, 1 subnets O IA 2.2.2.2 [110/129] via 25.0.0.2, 00:03:51, Serial1 3.0.0.0/32 is subnetted, 1 subnets O 3.3.3.3 [110/65] via 25.0.0.2, 00:03:51, Serial1 Router2#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/32 is subnetted, 1 subnets O IA 1.1.1.1 [110/129] via 50.0.0.1, 00:06:01, Serial0/0 C 50.0.0.0/8 is directly connected, Serial0/0 C 2.0.0.0/8 is directly connected, Loopback0 3.0.0.0/32 is subnetted, 1 subnets O IA 3.3.3.3 [110/65] via 50.0.0.1, 00:06:03, Serial0/0 O IA 25.0.0.0/8 [110/192] via 50.0.0.1, 00:06:01, Serial0/0 Router2#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O IA 1.1.1.1 [110/129] via 50.0.0.1, 00:06:07, Serial0/0 3.0.0.0/32 is subnetted, 1 subnets O IA 3.3.3.3 [110/65] via 50.0.0.1, 00:06:09, Serial0/0

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O IA 25.0.0.0/8 [110/192] via 50.0.0.1, 00:06:07, Serial0/0 Router3#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E – EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route Gateway of last resort is not set 1.0.0.0/32 is subnetted, 1 subnets O IA 1.1.1.1 [110/65] via 25.0.0.1, 00:08:15, Serial1 C 50.0.0.0/8 is directly connected, Serial0 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/65] via 50.0.0.2, 00:08:25, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 C 25.0.0.0/8 is directly connected, Serial1 Router3#sh ip route ospf 1.0.0.0/32 is subnetted, 1 subnets O IA 1.1.1.1 [110/65] via 25.0.0.1, 00:08:23, Serial1 2.0.0.0/32 is subnetted, 1 subnets O 2.2.2.2 [110/65] via 50.0.0.2, 00:08:33, Serial0 NEIGHBOR & DATABASE TABLES : Router1#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 FULL/ - 00:00:33 25.0.0.2 Serial1 The below database table shows database of all connected areas – Router1 is connected to area 0 & area 1 and hence both are displayed. “Summary Net Link States” represent the Link State Advertisements from other areas. Router1#sh ip ospf database OSPF Router with ID (1.1.1.1) (Process ID 1) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 256 0x80000003 0x5EFB 2 3.3.3.3 3.3.3.3 255 0x80000005 0xD061 3 Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 1.1.1.1 1.1.1.1 1487 0x80000001 0x47EC

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2.2.2.2 3.3.3.3 256 0x80000001 0x5F88 50.0.0.0 3.3.3.3 256 0x80000002 0xA5D7 Router Link States (Area 1) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 1486 0x80000002 0xD152 1 Summary Net Link States (Area 1) Link ID ADV Router Age Seq# Checksum 2.2.2.2 1.1.1.1 252 0x80000001 0x1E91 3.3.3.3 1.1.1.1 253 0x80000001 0x6D7E 25.0.0.0 1.1.1.1 253 0x80000002 0x2876 50.0.0.0 1.1.1.1 253 0x80000001 0x66DF Router2#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 3.3.3.3 1 FULL/ - 00:00:31 50.0.0.1 Serial0/0 Router2#sh ip ospf database OSPF Router with ID (2.2.2.2) (Process ID 2) Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 2.2.2.2 2.2.2.2 406 0x80000003 0x00D036 3 3.3.3.3 3.3.3.3 400 0x80000004 0x009288 2 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 1.1.1.1 3.3.3.3 390 0x80000001 0x008D5E 3.3.3.3 3.3.3.3 1620 0x80000001 0x00AE75 25.0.0.0 3.3.3.3 390 0x80000002 0x00EBAA Router3#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL/ - 00:00:38 25.0.0.1 Serial1 2.2.2.2 1 FULL/ - 00:00:32 50.0.0.2 Serial0 Router3#sh ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 3) Router Link States (Area 0) Link ID ADV Router Age Seq# Checksum Link count 1.1.1.1 1.1.1.1 532 0x80000003 0x5EFB 2 3.3.3.3 3.3.3.3 530 0x80000005 0xD061 3

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Summary Net Link States (Area 0) Link ID ADV Router Age Seq# Checksum 1.1.1.1 1.1.1.1 1763 0x80000001 0x47EC 2.2.2.2 3.3.3.3 531 0x80000001 0x5F88 50.0.0.0 3.3.3.3 531 0x80000002 0xA5D7 Router Link States (Area 2) Link ID ADV Router Age Seq# Checksum Link count 2.2.2.2 2.2.2.2 538 0x80000003 0xD036 3 3.3.3.3 3.3.3.3 532 0x80000004 0x9288 2 Summary Net Link States (Area 2) Link ID ADV Router Age Seq# Checksum 1.1.1.1 3.3.3.3 521 0x80000001 0x8D5E 3.3.3.3 3.3.3.3 1753 0x80000001 0xAE75 25.0.0.0 3.3.3.3 522 0x80000002 0xEBAA Router1#sh ip ospf interface Serial1 is up, line protocol is up Internet Address 25.0.0.1/8, Area 0 Process ID 1, Router ID 1.1.1.1,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:01 Index 1/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 3.3.3.3 Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 1.1.1.1/8, Area 1 Process ID 1, Router ID 1.1.1.1, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host Router2#sh ip ospf interface Serial0/0 is up, line protocol is up Internet Address 50.0.0.2/8, Area 2 Process ID 2, Router ID 2.2.2.2,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:08 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 3.3.3.3 Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 2.2.2.2/8, Area 2 Process ID 2, Router ID 2.2.2.2, Network Type LOOPBACK, Cost: 1

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Loopback interface is treated as a stub Host Router3#sh ip ospf interface Serial1 is up, line protocol is up Internet Address 25.0.0.2/8, Area 0 Process ID 3, Router ID 3.3.3.3,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:00 Index 2/2, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 1, maximum is 2 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 1.1.1.1 Suppress hello for 0 neighbor(s) Loopback0 is up, line protocol is up Internet Address 3.3.3.3/8, Area 0 Process ID 3, Router ID 3.3.3.3, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host Serial0 is up, line protocol is up Internet Address 50.0.0.1/8, Area 2 Process ID 3, Router ID 3.3.3.3,Network Type POINT_TO_POINT, Cost: 64 Transmit Delay is 1 sec, State POINT_TO_POINT, Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:00 Index 2/3, flood queue length 0 Next 0x0(0)/0x0(0) Last flood scan length is 2, maximum is 2 Last flood scan time is 0 msec, maximum is 0 msec Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 2.2.2.2 Suppress hello for 0 neighbor(s)

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CDP Cisco Discovery Protocol (CDP) helps us to gather details regarding Cisco Devices (All Devices) directly connected to the device on which we are running the protocol. This is a Cisco Proprietory Protocol.

To view CDP information Router1#sh cdp Global CDP information: Sending CDP packets every 60 seconds Sending a holdtime value of 180 seconds Sending CDPv2 advertisements is enabled To find out brief details regarding directly connected CISCO Devices, Router1#sh cdp neighbors Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater Device ID Local Intrfce Holdtme Capability Platform Port ID FRSW Ser 0 167 R 2520 Ser 0 For detailed neighbor information, Router1#sh cdp neighbors detail ------------------------- Device ID: FRSW (neighbor’s Hostname) Entry address(es): IP address: 100.0.0.245 (Interface IP address) Platform: cisco 2520, Capabilities: Router

(Indicates neighbor is a router) Interface: Serial0, Port ID (outgoing port): Serial0 Holdtime : 159 sec Version : Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JK8OS-L), Version 12.2(1d), RELEASE SOFTWARE (fc1) Copyright (c) 1986-2002 by cisco Systems, Inc. advertisement version: 2 (CDP version number) Let’s view the same on the other router FRSW#sh cdp neighbors Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r - Repeater

S0 100.0.0.245

S0 100.0.0.2 Router1 FRSW

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Device ID Local Intrfce Holdtme Capability Platform Port ID Router1 Ser 0 137 R 2500 Ser 0 FRSW#sh cdp neighbors detail ------------------------- Device ID: Router1 Entry address(es): IP address: 100.0.0.2 Platform: cisco 2500, Capabilities: Router Interface: Serial0, Port ID (outgoing port): Serial0 Holdtime : 132 sec Version : Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JK8OS-L), Version 12.2(1d), RELEASE SOFTWARE (fc1) Copyright (c) 1986-2002 by cisco Systems, Inc. advertisement version: 2

Router boot sequence

We can make the router boot from different sources by changing the boot field (last 4 bits) in the 16 bit config register. The various possibilities are as under. 0x2100 ROMMON - for diagnostic 0x2101 Mini IOS – in ROM 0x2102 Boot from first file in Flash (default value) 0x2102 – 0x210F with Boot System commands defined can make the router boot from any other file in Flash / tftp server (remote boot). 0x indicates it’s a hexa value When we normally boot a router (from flash), we should see the default config-register value 0x2102 from the “show version” output. Router1#sh version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JK8OS-L), Version 12.2(1d), RELEASE SOFTWARE (fc1) Copyright (c) 1986-2002 by cisco Systems, Inc. Compiled Sun 03-Feb-02 22:01 by srani Image text-base: 0x0307EEE0, data-base: 0x00001000 ROM: System Bootstrap, Version 11.0(10c), SOFTWARE BOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1) Router1 uptime is 10 minutes System returned to ROM by power-on System image file is "flash:c2500-jk8os-l.122-1d.bin"

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cisco 2500 (68030) processor (revision N) with 14336K/2048K bytes of memory. Processor board ID 21580975, with hardware revision 00000000 Bridging software. X.25 software, Version 3.0.0. SuperLAT software (copyright 1990 by Meridian Technology Corp). TN3270 Emulation software. 1 Ethernet/IEEE 802.3 interface(s) 2 Serial network interface(s) 32K bytes of non-volatile configuration memory. 16384K bytes of processor board System flash (Read ONLY) Configuration register is 0x2102 Router1# To change the config register value and make it boot from ROM Monitor mode, the below command is used. Router1(config)#config-register 0x2100 Router1(config)#^Z Router1# reload (warm boot) System configuration has been modified. Save? [yes/no]: hit the key “Y” Proceed with reload? [confirm]hit the return key Cisco Internetwork Operating System Software Copyright (c) 1986-2002 by cisco Systems, Inc. > This prompt indicates that the router has booted in ROMMON. This offers only character based support, not command based support. I for initialize O for config mode R for register H for help ? for help From ROMMON mode, to change the config register value to 0x2101 (to make it boot from mini IOS), let’s use the below syntax > o/r 0x2101 (to change config register value) > I (to initialize - reboot) The router reboots… Cisco Internetwork Operating System Software Copyright (c) 1986-2002 by cisco Systems, Inc Router1#(boot)> This is the mini IOS prompt and this works much like our regular mode. The major difference is that this mode doesn‟t support many commands.

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IOS Backup

Consider the above scenario. We’d like to take a back up of our IOS image from the router to the tftp server. The process is very simple as demonstrated below. First let’s view our IOS file stored in the flash. Router1#sh version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JK8OS-L), Version 12.2(1d), RELEASE SOFTWARE (fc1) Copyright (c) 1986-2002 by cisco Systems, Inc. Compiled Sun 03-Feb-02 22:01 by srani Image text-base: 0x0307EEE0, data-base: 0x00001000 ROM: System Bootstrap, Version 11.0(10c), SOFTWARE BOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1) AccessSrv uptime is 3 minutes System returned to ROM by power-on System image file is "flash:/c2500-jk8os-l.122-1d.bin" cisco 2509 (68030) processor (revision M) with 14336K/2048K bytes of memory. Processor board ID 22068840, with hardware revision 00000000 Bridging software. X.25 software, Version 3.0.0. SuperLAT software (copyright 1990 by Meridian Technology Corp). TN3270 Emulation software. 1 Ethernet/IEEE 802.3 interface(s) 2 Serial network interface(s) 8 terminal line(s) 32K bytes of non-volatile configuration memory. 16384K bytes of processor board System flash (Read ONLY) Configuration register is 0x2102 Backing up is using the command “copy flash tftp”. We’ll be able to see a series of exclamation marks on the console screen indicating that back up is in progress.

E0 10.0.0.100

TFTP SERVER 10.0.0.2

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Router1#copy flash tftp Source filename []? c2500-jk8os-l.122-1d.bin Address or name of remote host []? 10.0.0.2 Destination filename [c2500-jk8os-l.122-1d.bin]? .!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! <process omitted> 15686 Bytes transferred successfully on Friday Jan 13 14:41:03 2006 On the host running tftp server, we’ll be able to see a series of “#” during the backup process.

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ACCESS CONTROL LIST – ACL

A company - Madras Plastic & Co. has 2 offices one located in Chennai and another in salem. Chennai office is the Head Office and salem a branch office. They have some ftp and web servers at their Head Office but restrictions are to be imposed (as listed below) for users from Salem office. Certain other restrictions on Chennai LAN users are also to be implemented as below. 1. Salem‟s System Admin does not want to provide access (to his Network) to the Chennai user 10.0.0.4. 2. Only 172.16.0.2 must be allowed to download from the company‟s FTP server 3. 172.16.0.3 must not be allowed access to web server located in head office. 4. Chennai Network users are not allowed to telnet Salem router. So we are going to configure some Access-Control-list on these two routers. This is done in two steps. (i)Create Access Lists (ACL) in Global Configuration Mode. (ii)Apply them to Router interfaces specifying direction. Let‟s first understand how to create Standard and Extended access list Standard (In global configuration mode) Chennai(Config)# access-list < no. > permit / deny < sources network/ip address> <wild card mask>

Standard access list number range is 1 to 99. Wild card mask is just the opposite of SubNet Mask

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Extended (In global configuration mode) Chennai(Config)# access-list < no.> permit / deny < protocol > < sources network/ip address > < wild card mask> < destination network/ip address > <wild card mask> eq < port no./ service name >

extended access list number range is 100 to 199 Specify both source & destination address Specify protocol Specify particular application port no. for filtering

Implementation command at specific interface mode Chennai(Config-if)# ip access-group <access-list no.> <in / out> Note : default is out Now we‟ll implement the security policy. Condition 1. 10.0.0.4 should not access salem office network – this is a policy to be defined in Salem router using a standard Access List. Salem(Config)#access-list 10 deny 10.0.0.4 0.0.0.0 Salem(Config)#access-list 10 permit any We can configure the same command using the keyword “Host” to represent a single computer – in which case the Wild Card Mask is not required. Salem(Config)#access-list 10 deny host 10.0.0.4 Salem(Config)#access-list 10 permit any (The “permit any” command at the last is necessary to override the “implicit deny” of ACLs) As the second step we‟ll now apply this ACL as “outbound” (leaving the router) on interface Ethernet 0. This is because the traffic has to be filtered when it „enters the Salem LAN‟ and Standard ACLs are applied closest to the destination Network. Salem(config-if)#ip access-group 10 out Lets check show running-config output Salem# show running-config ! interface Ethernet0 description connected to Salem Local Area Network ip address 10.0.0.1 255.0.0.0 ip access-group 10 out ! <some output omitted> ! access-list 10 deny 10.0.0.4 0.0.0.0 access-list 10 permit any

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Our second task is to control access to FTP & Web Servers. Only Host 172.16.0.2 can download from FTP server(port 20)& Host 172.16.0.3 cannot access webserver (WWW – port 80). Chennai(config)#access-list 100 permit tcp host 172.16.0.2 host 10.0.0.2 eq ftp Chennai(config)#access-list 100 deny tcp any host 10.0.0.2 eq ftp Chennai(config)#access-list 100 deny tcp host 172.16.0.3 host 10.0.0.3 eq 80 Chennai(config)#access-list 100 permit ip any any Observe, we have used ftp in the first case & port no. 80 in the next. Both forms are acceptable. This access-list is applied on interface s0 as “inbound” access-list as we are trying to control traffic entering the router. Chennai(Config)#interface s0 Chennai(config-if)#ip access-group 100 in Let‟s check running-config Chennai# show running-config ! interface Serial0 description connected to public network ip address 200.0.0.5 255.255.255.252 ip access-group 100 in ! <some output omitted> ! Now let‟s see some ACL show commands Salem#show ip access-list Standard IP access list 10 deny 10.0.0.4 permit any Salem#show ip int Ethernet0 (displays application & direction of ACL ) Ethernet0 is up, line protocol is up Internet address is 172.16.0.1/16 Broadcast address is 255.255.255.255 Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is 10 Inbound access list is not set Proxy ARP is enabled Security level is default <output omitted> Chennai#show ip access-list Extended IP access list 100 deny tcp host 172.16.0.2 host 10.0.0.2 eq telnet deny tcp host 172.16.0.3 host 10.0.0.3 eq www

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deny tcp host 172.16.0.4 any permit ip any any Chennai#show ip int Serial0 Serial0 is up, line protocol is up Internet address is 200.0.0.5/30 Broadcast address is 255.255.255.255 Address determined by setup command MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is 100 Proxy ARP is enabled Security level is default Split horizon is enabled <output omitted> The final task is Chennai network users should not telnet salem router: Salem(config)#access-list 1 deny 10.0.0.0 0.255.255.255 Salem(config)#access-list 1 permit any where should we apply this ? Salem(config)#line vty 0 4 Salem(config-line)#access-class <access-list no.> in / out Yes! for telnet, we deploy the access-list on vty ! We use “access-class” and not “access-group” here. Command continues… Salem(config-line)#access-class 1 in Let‟s see some show commands for this configuration Salem#show ip access-list Standard IP access list 1 deny 10.0.0.0, wildcard bits 0.255.255.255 permit any Salem#show running-config ! line vty 0 4 access-class 1 in password cisco login Let‟s try telnetting from the host & see what happens.

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Observe the message in the above screen !

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NAT - NETWORK ADDRESS TRANSLATION

I) STATIC NAT : In the above scenario, an office uses private addresses for all its systems & requires to use static NAT (one-one fixed mapping) to communicate via Internet. The config. is as discussed below. The inside & outside Network Interfaces have to be defined for all NAT implementations. Let’s begin with this first. The syntax is simple and evident from the below config. Router1(config)#interface ethernet0 Router1(config-if)#ip add 10.0.0.1 255.0.0.0 Router1(config-if)#ip nat inside Router1(config-if)#no shutdown Router1(config)#interface serial 0 Router1(config-if)#ip add 200.0.0.1 255.0.0.0 Router1(config-if)#ip nat outside Router1(config-if)#no shutdown Next let’s define the static NAT using the command “ip nat inside source static <inside local address><inside global address>” and map our private address 10.0.0.2 to public address 200.0.0.10 Router1(config)#ip nat inside source static 10.0.0.2 200.0.0.10 Router1(config)#ip route 0.0.0.0 0.0.0.0 200.0.0.2

- default route defined to reach the ISP. The above is reflected in the running config too. Router1#show running-config Building configuration... Current configuration : 729 bytes ! hostname Router1

NAT

10.0.0.2 10.0.0.3 10.0.0.4 10.0.0.5

e0

10.0.0.1

Gateway for all computers is 10.0.0.1

s0

200.0.0.1 ISP

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! enable password cisco ! interface Ethernet0 ip address 10.0.0.1 255.0.0.0 ip nat inside ! interface Serial0 ip address 200.0.0.1 255.0.0.0 ip nat outside ! ip nat inside source static 10.0.0.2 200.0.0.10 ip route 0.0.0.0 0.0.0.0 200.0.0.2 ! line con 0 line aux 0 line vty 0 4 password cisco login ! end To view the NAT table, use the command “show ip nat translations” Router1#show ip nat translations Pro Inside global Inside local Outside local Outside global --- 200.0.0.10 10.0.0.2 --- --- To view inside & outside interfaces, use the command “show ip nat statistics” Router1#show ip nat statistics Total active translations: 1 (1 static, 0 dynamic; 0 extended) Outside interfaces: Serial1 Inside interfaces: Ethernet0 Hits: 4 Misses: 0 Expired translations: 0 Dynamic mappings: Router1#show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route

Gateway of last resort is not set C 200.0.0.0/8 is directly connected, Serial1 S 20.0.0.0/8 [1/0] via 200.0.0.2 C 10.0.0.0/8 is directly connected, Ethernet0

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To observe the Static NAT function, we’ll initiate a ping from host 10.0.0.2 to a remote host 20.0.0.10 and use “debug ip nat” to display the details. 10.0.0.2 must translate to 200.0.0.10 as per our NAT table. Router1#debug ip nat 01:54:09: NAT*: s=10.0.0.2->200.0.0.10, d=20.0.0.10 [63104] ICMP echo request packet 01:54:09: NAT*: s=20.0.0.10, d=200.0.0.10->10.0.0.2 [274]

ICMP echo reply packet

“s” stands for source IP “->” means translated to “d” stands for destination IP As ping sends echo request 4 times & receives an equal no. of replies, we see the above repeated 3 more times. 01:54:10: NAT*: s=10.0.0.2->200.0.0.10, d=20.0.0.10 [63107] 01:54:10: NAT*: s=20.0.0.10, d=200.0.0.10->10.0.0.2 [275] 01:54:11: NAT*: s=10.0.0.2->200.0.0.10, d=20.0.0.10 [63111] 01:54:11: NAT*: s=20.0.0.10, d=200.0.0.10->10.0.0.2 [276] 01:54:12: NAT*: s=10.0.0.2->200.0.0.10, d=20.0.0.10 [63114] 01:54:12: NAT*: s=20.0.0.10, d=200.0.0.10->10.0.0.2 [273]

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II) DYNAMIC NAT : For Dynamic NAT too we’ll use the same scenario. Let’s configure the inside & outside interface first. Router1(config)#interface ethernet0 Router1(config-if)#ip add 10.0.0.1 255.0.0.0 Router1(config-if)#ip nat inside Router1(config-if)#no shutdown Router1(config)#interface serial 0 Router1(config-if)#ip add 200.0.0.1 255.0.0.0 Router1(config-if)#ip nat outside Router1(config-if)#no shutdown Router1(config)#ip route 0.0.0.0 0.0.0.0 serial 0 We’ll now configure the pool of Public IPs using the command “ip nat pool <pool name><start IP><end IP>netmask<subnet Mask> Router1(config)#ip nat pool RJP 200.0.0.1 200.0.0.2 netmask 255.0.0.0 We’ll now have to define a list of our internal IP address using accesslist (purely for the purpose of listing the IP addresses & not for any Security configuration). We’ll define all 10.0.0.0 network IPs in our list. Router1(config)#Access-list 1 permit 10.0.0.0 0.255.255.255 Finally the list has to be mapped to the pool using the command “ip nat inside source list <list name> pool <pool name>” Router1(config)#ip nat inside source list 1 pool RJP Here we have many internal IP addresses and only 2 valid public IP addresses for NATing - this means only 2 internal hosts can dynamically associate with the pool addresses simultaneously and communicate via internet. Only when released after a timeout (default 24 hrs), the others may be able to use the same pool IPs. Router1#sh run Building configuration... Current configuration : 811 bytes ! hostname Router1 ! enable password cisco ! interface Ethernet0 ip address 10.0.0.1 255.0.0.0 ip nat inside ! interface Serial0 ip address 200.0.0.1 255.0.0.0 ip nat outside ! ip nat pool RJP 200.0.0.1 200.0.0.2 netmask 255.0.0.0 ip nat inside source list 1 pool RJP !

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ip route 0.0.0.0 0.0.0.0 Serial0 ! access-list 1 permit 10.0.0.0 0.255.255.255 ! line con 0 line aux 0 line vty 0 4 password cisco login ! End Router1#sh ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route

Gateway of last resort is 0.0.0.0 to network 0.0.0.0 C 10.0.0.0/8 is directly connected, Ethernet0 S* 0.0.0.0/0 is directly connected, Serial0 C 200.0.0.0/8 is directly connected, Serial0 The NAT table is empty before any traffic flow. Router1#sh ip nat translations <The translation table is empty> Additional config. details are seen in “sh ip nat statistics” command Router1#sh ip nat stat Router1#sh ip nat statistics Total active translations: 0 (0 static, 0 dynamic; 0 extended) Outside interfaces: Serial0 Inside interfaces: Ethernet0 Hits: 0 Misses: 0 Expired translations: 0 Dynamic mappings: -- Inside Source access-list 1 pool RJP refcount 0 pool RJP: netmask 255.0.0.0 start 200.0.0.1 end 200.0.0.2 type generic, total addresses 2, allocated 0 (0%), misses 0 Let’s try initiating ping from 3 internal hosts simultaneously. Router1#debug ip nat IP NAT debugging is on Router1# 01:31:49: NAT: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13426] 01:31:49: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13426]

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01:31:50: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13427] 01:31:50: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13427] 01:31:51: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13432] 01:31:51: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13432] 01:31:52: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13437] 01:31:52: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13437] 01:32:10: NAT: s=10.0.0.3->200.0.0.2, d=20.0.0.1 [1473] 01:32:10: NAT*: s=20.0.0.1, d=200.0.0.2->10.0.0.3 [1473] 01:32:11: NAT*: s=10.0.0.3->200.0.0.2, d=20.0.0.1 [1474] 01:32:11: NAT*: s=20.0.0.1, d=200.0.0.2->10.0.0.3 [1474] 01:32:12: NAT*: s=10.0.0.3->200.0.0.2, d=20.0.0.1 [1475] 01:32:12: NAT*: s=20.0.0.1, d=200.0.0.2->10.0.0.3 [1475] 01:32:13: NAT*: s=10.0.0.3->200.0.0.2, d=20.0.0.1 [1476] 01:32:13: NAT*: s=20.0.0.1, d=200.0.0.2->10.0.0.3 [1476] 01:34:42:NAT:translation failed(A), dropping packet s=10.0.0.4 d=20.0.0.1 01:34:48: NAT: translation failed (A), dropping packet s=10.0.0.4 d=20.0.0.1 01:34:49: NAT: translation failed (A), dropping packet s=10.0.0.4 d=20.0.0.1 01:34:50: NAT: translation failed (A), dropping packet s=10.0.0.4 d=20.0.0.1 The third translation fails as there are no free IPs in the pool as the first 2 pings have exhausted the available pool IPs. Router1#sh ip nat translations Pro Inside global Inside local Outside local Outside global --- 200.0.0.1 10.0.0.2 --- --- --- 200.0.0.2 10.0.0.3 --- --- Router1#sh ip nat statistics Total active translations: 2 (0 static, 2 dynamic; 0 extended) Outside interfaces: Serial0 Inside interfaces: Ethernet0 Hits: 8 Misses: 4 Expired translations: 0 Dynamic mappings: -- Inside Source access-list 1 pool RJP refcount 4 pool RJP: netmask 255.0.0.0 start 200.0.0.1 end 200.0.0.2 type generic, total addresses 2, allocated 2 (100%), misses 4 It’s possible to remove all the dynamic entries in the Nat table using the command “clear ip nat translations *”.

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III) NAT with PAT : This is for simultaneous use of single (or more than one) Public IP by many internal hosts. Port numbers are used for this purpose. Consider the same scenario as before - the only difference in configuration would be the “overload” keyword used in the list-pool mapping. Router1(config)#ip nat pool RJP 200.0.0.1 200.0.0.1 netmask 255.0.0.0 Router1(config)#Access-list 1 permit 10.0.0.0 0.255.255.255 Router1(config)#ip nat inside source list 1 pool RJP overload Router1#sh run Building configuration... Current configuration : 820 bytes ! hostname Router1 ! enable password cisco ! interface Ethernet0 ip address 10.0.0.1 255.0.0.0 ip nat inside ! interface Serial0 ip address 200.0.0.1 255.0.0.0 ip nat outside ! ip nat pool RJP 200.0.0.1 200.0.0.1 netmask 255.0.0.0 ip nat inside source list 1 pool RJP overload ip route 0.0.0.0 0.0.0.0 Serial0 ! access-list 1 permit 10.0.0.0 0.255.255.255 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! End Router1#sh ip nat translations <The table is empty> Router1#sh ip nat statistics Total active translations: 0 (0 static, 0 dynamic; 0 extended) Outside interfaces: Serial0 Inside interfaces: Ethernet0 Hits: 28 Misses: 4 Expired translations: 0 Dynamic mappings: -- Inside Source access-list 1 pool RJP refcount 0

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pool RJP: netmask 255.0.0.0 start 200.0.0.1 end 200.0.0.1 type generic, total addresses 1, allocated 0 (0%), misses 0 Allocated 0 implies unused pool addresses. Initiating simultaneous ping from multiple hosts results in the below debug output. Router1#debug ip nat IP NAT debugging is on Router1# 01:31:49: NAT: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13426] 01:31:49: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13426] 01:31:50: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13427] 01:31:50: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13427] 01:31:51: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13432] 01:31:51: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13432] 01:31:52: NAT*: s=10.0.0.2->200.0.0.1, d=20.0.0.1 [13437] 01:31:52: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.2 [13437] 01:32:10: NAT: s=10.0.0.3->200.0.0.1, d=20.0.0.1 [1473] 01:32:10: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.3 [1473] 01:32:11: NAT*: s=10.0.0.3->200.0.0.1, d=20.0.0.1 [1474] 01:32:11: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.3 [1474] 01:32:12: NAT*: s=10.0.0.3->200.0.0.1, d=20.0.0.1 [1475] 01:32:12: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.3 [1475] 01:32:13: NAT*: s=10.0.0.3->200.0.0.1, d=20.0.0.1 [1476] 01:32:13: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.3 [1476] 01:32:32: NAT: s=10.0.0.4->200.0.0.1, d=20.0.0.1 [1492] 01:32:32: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.4 [1492] 01:32:37: NAT*: s=10.0.0.4->200.0.0.1, d=20.0.0.1 [1506] 01:32:37: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.4 [1506] 01:32:38: NAT*: s=10.0.0.4->200.0.0.1, d=20.0.0.1 [1511] 01:32:38: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.4 [1511] 01:32:39: NAT*: s=10.0.0.4->200.0.0.1, d=20.0.0.1 [1517] 01:32:39: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.4 [1517] 01:34:11: NAT: s=10.0.0.5->200.0.0.1, d=20.0.0.1 [1553] 01:34:11: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.5 [1553] 01:34:16: NAT*: s=10.0.0.5->200.0.0.1, d=20.0.0.1 [1566] 01:34:16: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.5 [1566] 01:34:17: NAT*: s=10.0.0.5->200.0.0.1, d=20.0.0.1 [1571] 01:34:17: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.5 [1571] 01:34:18: NAT*: s=10.0.0.5->200.0.0.1, d=20.0.0.1 [1577] 01:34:18: NAT*: s=20.0.0.1, d=200.0.0.1->10.0.0.1 [1577] Let’s see the clear difference in the NAT table - the last no. 512,513 etc is the port no. used to identify the internal host that originated the traffic. Router1#sh ip nat translations Pro Inside global Inside local Outside local Outside global icmp 200.0.0.1:512 10.0.0.2:512 20.0.0.1:512 20.0.0.1:512 icmp 200.0.0.1:513 10.0.0.3:513 20.0.0.1:513 20.0.0.1:513 icmp 200.0.0.1:514 10.0.0.4:514 20.0.0.1:514 20.0.0.1:514

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icmp 200.0.0.1:515 10.0.0.5:515 20.0.0.1:515 20.0.0.1:515 Router1#sh ip nat statistics Total active translations: 2 (0 static, 2 dynamic; 2 extended) Outside interfaces: Serial0 Inside interfaces: Ethernet0 Hits: 56 Misses: 8 Expired translations: 2 Dynamic mappings: -- Inside Source access-list 1 pool RJP refcount 2 pool RJP: netmask 255.0.0.0 start 200.0.0.1 end 200.0.0.1 type generic, total addresses 1, allocated 1 (100%), misses 0

Allocated 1 implies that the single pool IP has been used.

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WAN I) PPP & HDLC on Point to Point Link (Leased Line)

The default encapsulation on WAN Serial interface of a CISCO Router is HDLC. No further configuration is called for in a simple Point-to-Point Link. This is seen from the output of show interface command as below. Serial0 is up, line protocol is up Hardware is HD64570 Internet address is 200.0.0.1/8 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set Keepalive set (10 sec) If we are to connect to a non-Cisco Router or if we want to implement Authentication at the datalink layer, we need to go in for the standards based PPP encapsulation. Router1(config-if)#int s0 Router1(config-if)#ip add 200.0.0.1 255.0.0.0 Router1(config-if)#encapsulation ppp Router1(config-if)#clock rate 64000 Router1(config-if)#no shut Router1(config)#int loopback0 Router1(config-if)#ip add 5.5.5.5 255.0.0.0 Router1(config-if)#ip route 6.0.0.0 255.0.0.0 200.0.0.2 PPP supports optional Authentication with PAP or CHAP. We’ll begin with PAP first. a. PAP Authentication First, PAP Authentication has to be enabled in the interface config mode. Router1(config-if)#ppp authentication pap Next is to configure the other router’s name as the username and choose a common password (This alone is a global config command). Router1(config)#username Router2 password cisco “Router2” is the other router’s hostname & “cisco” is the password

5.5.5.5 R1 R3

s0 s0 L0 L0

R1 R2 6.6.6.6 200.0.0.1

200.0.0.2

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An additional command to inform this router’s name to the other router is also to be configured. Router1(config-if)#ppp pap sent-username Router1 password cisco Router1#sh int s0 Serial0 is up, line protocol is up Hardware is HD64570 Internet address is 200.0.0.1/8 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) LCP Open Open: IPCP, CDPCP Similar configuration has to be done with Router2 Verification : sh run, sh ip route & sh interface commands are used Router1#sh run Building configuration... Current configuration : 827 bytes ! hostname Router1 ! enable password cisco ! username Router2 password 0 cisco ! interface Loopback0 ip address 5.5.5.5 255.0.0.0 ! interface Serial0 ip address 200.0.0.1 255.0.0.0 encapsulation ppp ppp authentication pap ppp pap sent-username Router1 password 7 0822455D0A16 ! ip route 6.0.0.0 255.0.0.0 200.0.0.2 ! line con 0 line aux 0 line vty 0 4 password cisco login ! End Router2#sh run Building configuration... Current configuration : 891 bytes !

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hostname Router2 ! enable password cisco ! username Router1 password 0 cisco ! interface Loopback0 ip address 6.6.6.6 255.0.0.0 ! interface Serial0 ip address 200.0.0.2 255.0.0.0 clockrate 64000 encapsulation ppp ppp authentication pap ppp pap sent-username Router2 password 7 05080F1C2243 ! ip route 5.0.0.0 255.0.0.0 200.0.0.1 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter

area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route, o – ODR P - periodic downloaded static route

Gateway of last resort is not set 200.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 200.0.0.0/8 is directly connected, Serial0 C 200.0.0.2/32 is directly connected, Serial0 C 5.0.0.0/8 is directly connected, Loopback0 S 6.0.0.0/8 [1/0] via 200.0.0.2 Router2#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B – BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter

area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS- IS inter area * - candidate default, U - per-user static route,

o – ODR P - periodic downloaded static route Gateway of last resort is not set 200.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

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C 200.0.0.0/8 is directly connected, Serial0 C 200.0.0.1/32 is directly connected, Serial0 S 5.0.0.0/8 [1/0] via 200.0.0.1 C 6.0.0.0/8 is directly connected, Loopback0 Router2’s s0 is currently down. Output of s0 on router 1 displays “LCP closed” Router1#sh int s0 Serial0 is down, line protocol is down Hardware is HD64570 Internet address is 200.0.0.1/8 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) LCP Closed LCP closed indicates that the PPP link is not up yet. Using “Debug ppp authentication” command we can see the authentication process. It’s a 2-way handshake & bidirectional – both routers authenticating each other. Router1#debug ppp authentication PPP authentication debugging is on Router1# 00:24:50: Se0 PPP: Treating connection as a dedicated line 00:24:50: %LINK-3-UPDOWN: Interface Serial0, changed state to up 00:24:50: Se0 PAP: O AUTH-REQ id 1 len 18 from "Router1" 00:24:50: Se0 PAP: I AUTH-REQ id 2 len 18 from "Router2"

(Authentication request – username, password sent) 00:24:50: Se0 PAP: Authenticating peer Router2 00:24:50: Se0 PAP: O AUTH-ACK id 2 len 5 00:24:50: Se0 PAP: I AUTH-ACK id 1 len 5 (Authentication acknowledged – if username, password correct) 00:24:51: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up Once s0 of Router2 goes up, interface status shows “LCP open”. Wan link is now up. Router1#sh int s0 Serial0 is up, line protocol is up Hardware is HD64570 Internet address is 200.0.0.1/8 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set Keepalive set (10 sec) LCP Open

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b. CHAP Authentication The configuration is exactly like PAP only that “sent username…” is not required here. The below would show us the difference. Router1(config)#username Router2 password cisco Router1(config-if)#int s0 Router1(config-if)#ip add 200.0.0.1 255.0.0.0 Router1(config-if)#encapsulation ppp Router1(config-if)#ppp authentication chap Router1(config-if)#no shut Router2(config)#username Router1 password cisco Router2(config-if)#int s0 Router2(config-if)#ip add 200.0.0.2 255.0.0.0 Router2(config-if)#encapsulation ppp Router2(config-if)#ppp authentication chap Router2(config-if)#clock rate 64000 Router2(config-if)#no shut Router1#sh run Building configuration... Current configuration : 828 bytes ! hostname Router1 ! enable password cisco ! username Router2 password 0 cisco ! interface Loopback0 ip address 5.5.5.5 255.0.0.0 ! interface Serial0 ip address 200.0.0.1 255.0.0.0 encapsulation ppp ppp authentication chap <output omitted> Router2#sh run Building configuration... Current configuration : 963 bytes ! hostname Router2 ! enable password cisco ! username Router1 password 0 cisco !

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interface Loopback0 ip address 6.6.6.6 255.0.0.0 ! interface Serial0 ip address 200.0.0.2 255.0.0.0 clockrate 64000 encapsulation ppp ppp authentication chap <output omitted> Router1#sh ip route Gateway of last resort is not set 200.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 200.0.0.0/8 is directly connected, Serial0 C 200.0.0.2/32 is directly connected, Serial0 C 5.0.0.0/8 is directly connected, Loopback0 S 6.0.0.0/8 [1/0] via 200.0.0.2 Router2#sh ip route Gateway of last resort is not set 200.0.0.0/8 is variably subnetted, 2 subnets, 2 masks C 200.0.0.0/8 is directly connected, Serial0 C 200.0.0.1/32 is directly connected, Serial0 S 5.0.0.0/8 [1/0] via 200.0.0.1 C 6.0.0.0/8 is directly connected, Loopback0 VERIFICATION USING DEBUG COMMAND Router1#debug ppp authentication PPP authentication debugging is on 01:13:37: Se0 PPP: Treating connection as a dedicated line 01:13:37: Se0 CHAP: O CHALLENGE id 114 len 28 from "Router1" 01:13:37: Se0 CHAP: I CHALLENGE id 113 len 28 from "Router2" (A challenge is sent and another received) 01:13:37: Se0 CHAP: O RESPONSE id 113 len 28 from "Router1" 01:13:37: Se0 CHAP: I RESPONSE id 114 len 28 from "Router2" (Username, password is sent/received only after the challenge) 01:13:37: Se0 CHAP: O SUCCESS id 114 len 4 01:13:37: Se0 CHAP: I SUCCESS id 113 len 4 (If username & password are correct, authentication is successful) 01:13:38: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up The link now goes up ! Also note that the 3-way authentication process is bidirectional – both the routers authenticate each other.

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II) ISDN

Consider the above scenario where there are 2 offices of the same organization connected over a dial-up ISDN. The requirement being the ISDN connection should automatically come up whenever there is a traffic flow between the offices. This is referred to as Dial on Demand routing. This is a 3 step process

(i) Configure static route between the offices (ii) Define Interesting Traffic (iii) Configure Dialer

Step (i) Static route configuration Router4(config)#ip route 2.0.0.0 255.0.0.0 200.0.0.2 Router5(config)#ip route 1.0.0.0 255.0.0.0 200.0.0.1 Step (ii) Interesting Traffic definition using dialer list Router4(config)#dialer-list 1 protocol ip permit Router5(config)#dialer-list 2 protocol ip permit Note : If we want to selectively allow access for ISDN dial-up, we’ll then have to define the allowed IP addresses in an access-list and invoke in a dialer list as shown below. Config # dialer-list 1 protocol ip list <ACL no.> e.g. Router4(config)#dialer-list 1 protocol ip list 10 Router4(config)#access-list 10 permit 1.1.1.1 0.0.0.0 Step (iii) Dialer configuration We need to define the destination IP, number to be dialed & Interesting traffic list to be used. Router4(config-if)#dialer-group 1 Router4(config-if)#dialer map ip 200.0.0.2 252912 Router4(config-if)#no shut Router5(config-if)#dialer-group 2

1.1.1.1 R1 R3 BRI0

L0 L0 R4

R5 2.2.2.2 200.0.0.1

BRI0 ISDN Cloud R4 R5

ISDN no:252912 ISDN no:24731102

200.0.0.2

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Router5(config-if)#dialer map ip 200.0.0.1 24731102 Router5(config-if)#no shut As ISDN service providers use different types of ISDN switches, we need to specify the appropriate switch type in our router. In our case we’ll specify basic-net3. Router4(config)#isdn switch-type basic-net3 Router5(config)#isdn switch-type basic-net3 VERIFICATION Running config of routers 4 & 5 Router4#sh run Building configuration... Current configuration : 963 bytes ! hostname Router4 ! enable password cisco ! isdn switch-type basic-net3 ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! ! interface BRI0 ip address 200.0.0.1 255.255.255.0 dialer map ip 200.0.0.2 252912 dialer-group 1 isdn switch-type basic-net3 ! ip route 2.0.0.0 255.0.0.0 200.0.0.2 ! dialer-list 1 protocol ip permit ! line con 0 line aux 0 line vty 0 4 password cisco login ! End Router5#sh run Building configuration... Current configuration : 965 bytes ! hostname Router5 ! nable password cisco ! isdn switch-type basic-net3 ! interface Loopback0

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ip address 2.2.2.2 255.0.0.0 ! interface BRI0 ip address 200.0.0.2 255.255.255.0 dialer map ip 200.0.0.2 24731102 dialer-group 2 isdn switch-type basic-net3 ! ip route 1.0.0.0 255.0.0.0 200.0.0.1 ! dialer-list 2 protocol ip permit ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end When there is no traffic between the 2 offices, let’s find out the ISDN call status using the below 2 commands. Router4#sh isdn status Global ISDN Switchtype = basic-net3 ISDN BRI0 interface dsl 0, interface ISDN Switchtype = basic-net3 Layer 1 Status: ACTIVE Layer 2 Status: TEI = 64, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status: 0 Active Layer 3 Call(s) Active dsl 0 CCBs = 0 The Free Channel Mask: 0x80000003 Total Allocated ISDN CCBs = 0 The above would be the typical output if the configuration is correct. “0 Active layer 3” calls mean that ISDN link is not yet up. Router4#sh isdn active ----------------------------------------------------------------------- ISDN ACTIVE CALLS ----------------------------------------------------------------------- Call Calling Called Remote Seconds Seconds Seconds Charges Type Number Number Name Used Left Idle Units/Currency ----------------------------------------------------------------------- “sh ISDN active” output reveals that no ISDN call is in progress. Router4#sh int bri 0 BRI0 is up, line protocol is up (spoofing) Hardware is BRI Internet address is 200.0.0.1/24 MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255

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Encapsulation HDLC, loopback not set Router4#sh int bri 0:1 BRI0:1 is down, line protocol is down Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set Look at the difference – “sh int bri 0” shows the line protocol as up whereas “sh int bri 0:1” shows line protocol is down. This implies that BRI config is correct. Since there is no traffic, the BRI channel 1 is still down (Recall each BRI interface has 2 B channels). Similar outputs can be observed on Router5 as well. Router5#sh isdn active ----------------------------------------------------------------------- ISDN ACTIVE CALLS ----------------------------------------------------------------------- Call Calling Called Remote Seconds Seconds Seconds Charges Type Number Number Name Used Left Idle Units/Currency ----------------------------------------------------------------------- ----------------------------------------------------------------------- Router5#sh isdn status Global ISDN Switchtype = basic-net3 ISDN BRI0 interface dsl 0, interface ISDN Switchtype = basic-net3 Layer 1 Status: ACTIVE Layer 2 Status: TEI = 65, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status: 0 Active Layer 3 Call(s) Active dsl 0 CCBs = 0 The Free Channel Mask: 0x80000003 Total Allocated ISDN CCBs = 0 Router5#sh int bri 0 BRI0 is up, line protocol is up (spoofing) Hardware is BRI Internet address is 200.0.0.2/24 MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set Router5#sh int bri 0:1 BRI0:1 is down, line protocol is down Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set To check our DDR config, we’ll initiate ping from router4’s loopback & checkout if the WAN link comes up automatically.

110

Router4#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: 00:37:39: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 32/33/36 ms 00:37:40: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up Router4#sh isdn status Global ISDN Switchtype = basic-net3 ISDN BRI0 interface dsl 0, interface ISDN Switchtype = basic-net3 Layer 1 Status: ACTIVE Layer 2 Status: TEI = 64, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status: 1 Active Layer 3 Call(s) CCB:callid=8002, sapi=0, ces=1, B-chan=1, calltype=DATA Active dsl 0 CCBs = 1 The Free Channel Mask: 0x80000002 Total Allocated ISDN CCBs = 1 Observe the above output shows 1 Active Layer 3 calls now which was not the case earlier. “sh isdn active” gives us details of currently active calls. Router4#sh isdn active ----------------------------------------------------------------------- ISDN ACTIVE CALLS ----------------------------------------------------------------------- Call Calling Called Remote Seconds Seconds Seconds Charges Type Number Number Name Used Left Idle Units/Currency -----------------------------------------------------------------------Out 252912 14 107 12 0 Router4#sh int bri 0 BRI0 is up, line protocol is up (spoofing) Hardware is BRI Internet address is 200.0.0.1/24 MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set The BRI channel 1 protocol is also up now. Router4#sh int bri 0:1 BRI0:1 is up, line protocol is up Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation HDLC, loopback not set Debug output gives us greater details.

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Router4#debug dialer Dial on demand events debugging is on Router4#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: 00:41:30: BR0 DDR: Dialing cause ip (s=200.0.0.1, d=2.2.2.2) 00:41:30: BR0 DDR: Attempting to dial 252912 00:41:31: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up 00:41:31: BR0:1 DDR: dialer protocol up .!!!! Success rate is 80 percent (4/5), round-trip min/avg/max = 32/32/32 ms 00:41:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to up 00:43:32: BR0:1 DDR: idle timeout 00:43:32: BR0:1 DDR: disconnecting call 00:43:32: %ISDN-6-DISCONNECT: Interface BRI0:1 disconnected from 252912 , call lasted 121 seconds 00:43:32: %LINK-3-UPDOWN: Interface BRI0:1, changed state to down 00:43:33: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:1, changed state to down

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III) Frame-Relay

Frame-Relay is typically a PVC and the configurations are fairly simple. Once encapsulation Frame-relay is configured on the WAN Serial Interface, it supports both Multipoint & Point-to-Point connections without any further configuration. Router1(config)#int loopback0 Router1(config-if)#ip add 1.1.1.1 255.0.0.0 Router1(config-if)#int s0 Router1(config-if)#ip add 150.0.0.1 255.255.0.0 Router1(config-if)#encapsulation frame-relay Router2(config)#int loopback0 Router2(config-if)#ip add 2.2.2.2 255.0.0.0 Router2(config-if)#int s0/0 Router2(config-if)#ip add 150.0.0.2 255.255.0.0 Router2(config-if)#encapsulation frame-relay As usual, let’s view the running config & routing tables of both the routers. Router1#sh run Building configuration... Current configuration : 832 bytes ! hostname Router1 ! enable password cisco ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial0 ip address 150.0.0.1 255.255.0.0 encapsulation frame-relay ! router rip network 1.0.0.0 network 150.0.0.0 line con 0 transport input none line aux 0

FR Cloud

s0

150.0.0.1 s0

R1 L0

L0 1.1.1.1

2.2.2.2

Point-to-Point WAN configuration

150.0.0.2

R2

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line vty 0 4 password cisco login ! End Router2#sh run Building configuration... Current configuration : 791 bytes ! hostname "Router2" ! enable password cisco ! interface Loopback0 ip address 2.2.2.2 255.0.0.0 ! interface Serial0/0 ip address 150.0.0.2 255.255.0.0 encapsulation frame-relay no fair-queue ! route rip network 2.0.0.0 network 150.0.0.0 ! line con 0 line aux 0 line vty 0 4 password cisco login ! End Router1#sh ip route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 R 2.0.0.0/8 [120/1] via 150.0.0.2, 00:00:17, Serial0 R 3.0.0.0/8 [120/1] via 150.0.0.3, 00:00:08, Serial0 C 150.0.0.0/16 is directly connected, Serial0 Router2#sh ip route Gateway of last resort is not set R 1.0.0.0/8 [120/1] via 150.0.0.1, 00:00:02, Serial0/0 C 2.0.0.0/8 is directly connected, Loopback0 R 3.0.0.0/8 [120/2] via 150.0.0.1, 00:00:02, Serial0/0 C 150.0.0.0/16 is directly connected, Serial0/0 If the frame-Relay link were up, we will be able to see the PVC status as active & we’ll also be able to view the DLCI number. Router1#sh frame-relay pvc PVC Statistics for interface Serial0 (Frame Relay DTE)

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Active Inactive Deleted Static Local 1 0 0 0 Switched 0 0 0 0 Unused 0 0 0 0 DLCI = 100,DLCI USAGE = LOCAL,PVC STATUS = ACTIVE,INTERFACE = Serial0 input pkts 41 output pkts 50 in bytes 4032 out bytes 4806 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 12 out bcast bytes 970 pvc create time 00:40:28, last time pvc status changed 00:37:30 To view the DLCI no. mapping, use the below command Router1#sh frame-relay map Serial0 (up): ip 150.0.0.2 dlci 100(0x64,0x1840), dynamic, broadcast,, status defined, active The LMI type can be seen as below Router1#sh frame-relay lmi LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO Invalid Unnumbered info 0 Invalid Prot Disc 0 Invalid dummy Call Ref 0 Invalid Msg Type 0 Invalid Status Message 0 Invalid Lock Shift 0 Invalid Information ID 0 Invalid Report IE Len 0 Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 244 Num Status msgs Rcvd 245 Num Update Status Rcvd 0 Num Status Timeouts 0 Let’s see Router2’s outputs also. Router2#sh frame-relay pvc PVC Statistics for interface Serial0/0 (Frame Relay DTE) Active Inactive Deleted Static Local 1 0 0 0 Switched 0 0 0 0 Unused 0 0 0 0 DLCI = 200, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0 input pkts 60 output pkts 50 in bytes 5966 out bytes 5158 dropped pkts 0 in pkts dropped 0 out pkts dropped 0 out bytes dropped 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 20 out bcast bytes 2038 pvc create time 00:42:25, last time pvc status changed 00:42:05 Router2#sh frame-relay map Serial0/0 (up): ip 150.0.0.1 dlci 200(0xC8,0x3080), dynamic,

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broadcast,, status defined, active Router2#sh frame-relay lmi LMI Statistics for interface Serial0/0(Frame Relay DTE)LMI TYPE = CISCO Invalid Unnumbered info 0 Invalid Prot Disc 0 Invalid dummy Call Ref 0 Invalid Msg Type 0 Invalid Status Message 0 Invalid Lock Shift 0 Invalid Information ID 0 Invalid Report IE Len 0 Invalid Report Request 0 Invalid Keep IE Len 0 Num Status Enq. Sent 256 Num Status msgs Rcvd 257 Num Update Status Rcvd 0 Num Status Timeouts 0 NOTE : The “show frame-relay PVC” command would show “inactive” entry if the remote WAN link were down. If the local link were down, it would have shown as “deleted”.

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Such a configuration would warrant configuring the HUB router with sub-interfaces as shown below. Router1(config)#int serial 0.1 This would be the normal sub-interface creation command. However, in a Frame-Relay environment, the sub-interface type also has to be specified during configuration. Router1(config)#int serial 0 Router1(config-if)#encapsulation frame-relay Router1(config)#int s0.1 ? multipoint Treat as a multipoint link point-to-point Treat as a point-to-point link Let’s create 2 point-to-point sub-interfaces Router1(config)#int s0.1 point-to-point Router1(config-subif)#ip add 150.0.0.1 255.255.0.0 Router1(config-subif)#exit Router1(config)#int s0.2 point-to-point Router1(config-subif)#ip add 160.0.0.1 255.255.0.0 Router1(config-subif)# Once created, we also need to associate appropriate DLCI to the sub-interfaces on the HUB Router. Router1(config)#int s0.1 Router1(config-subif)#frame-relay interface-dlci 100 Router1(config-fr-dlci)#exit Router1(config-subif)#exit Router1(config)#int s0.2 Router1(config-subif)#frame-relay interface-dlci 300 Router1(config-fr-dlci)#exit Router1(config-subif)#exit Router1#sh run Building configuration... Current configuration : 966 bytes

FR Cloud

S0.1

R3

150.0.0.1

s0

s0

160.0.0.2

150.0.0.2

R1

R2

L0

L0

L0

1.1.1.1

2.2.2.2

3.3.3.3

HUB & SPOKE configuration Diagram

S0.2 160.0.0.1

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! hostname Router1 ! enable password cisco ! interface Loopback0 ip address 1.1.1.1 255.0.0.0 ! interface Serial0 no ip address encapsulation frame-relay ip split-horizon ! interface Serial0.1 point-to-point ip address 150.0.0.1 255.255.0.0 frame-relay interface-dlci 100 ! interface Serial0.2 point-to-point ip address 160.0.0.1 255.255.0.0 frame-relay interface-dlci 300 ! router rip network 1.0.0.0 network 150.0.0.0 network 160.0.0.0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router1#sh ip route Gateway of last resort is not set C 1.0.0.0/8 is directly connected, Loopback0 R 2.0.0.0/8 [120/1] via 150.0.0.2, 00:00:13, Serial0.1 R 3.0.0.0/8 [120/1] via 160.0.0.2, 00:00:27, Serial0.2 C 160.0.0.0/16 is directly connected, Serial0.2 C 150.0.0.0/16 is directly connected, Serial0.1 We’ll now be able to see 2 active PVCs on the HUB Router. Router1#sh frame-relay pvc PVC Statistics for interface Serial0 (Frame Relay DTE) Active Inactive Deleted Static Local 2 0 0 0 Switched 0 0 0 0 Unused 0 0 0 0 DLCI = 100, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0.1

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input pkts 53 output pkts 59 in bytes 4998 out bytes 7384 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 46 out bcast bytes 6156 pvc create time 00:18:45, last time pvc status changed 00:18:45 DLCI = 300, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0.2 input pkts 20 output pkts 48 in bytes 1730 out bytes 7118 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 33 out bcast bytes 5558 pvc create time 00:18:47, last time pvc status changed 00:18:47 Router1#sh frame-relay map Serial0.2 (up): point-to-point dlci, dlci 300(0x12C,0x48C0), broadcast status defined, active Serial0.1 (up): point-to-point dlci, dlci 100(0x64,0x1840), broadcast status defined, active Router2#sh run Building configuration... Current configuration : 766 bytes ! hostname "Router2" ! enable password cisco ! interface Loopback0 ip address 2.2.2.2 255.0.0.0 ! interface Serial0/0 ip address 150.0.0.2 255.255.0.0 encapsulation frame-relay no fair-queue ! router rip network 2.0.0.0 network 150.0.0.0 ! <output omitted> Other Routers display similar details Router2#sh ip route Gateway of last resort is not set R 1.0.0.0/8 [120/1] via 150.0.0.1, 00:00:16, Serial0/0 C 2.0.0.0/8 is directly connected, Loopback0 R 3.0.0.0/8 [120/2] via 150.0.0.1, 00:00:16, Serial0/0 R 160.0.0.0/16 [120/1] via 150.0.0.1, 00:00:16, Serial0/0

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C 150.0.0.0/16 is directly connected, Serial0/0 Router2#sh frame-relay pvc PVC Statistics for interface Serial0/0 (Frame Relay DTE) Active Inactive Deleted Static Local 1 0 0 0 Switched 0 0 0 0 Unused 0 0 0 0 DLCI = 200, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0 input pkts 145 output pkts 125 in bytes 16384 out bytes 12708 dropped pkts 0 in pkts dropped 0 out pkts dropped 0 out bytes dropped 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 84 out bcast bytes 8432 pvc create time 01:12:11, last time pvc status changed 00:21:01 Router2#sh frame-relay map Serial0/0 (up): ip 150.0.0.1 dlci 200(0xC8,0x3080), dynamic, broadcast,, status defined, active Router3#sh run Building configuration... Current configuration : 815 bytes ! hostname Router3 ! enable password cisco ! interface Loopback0 ip address 3.3.3.3 255.0.0.0 ! interface Serial0 ip address 160.0.0.2 255.0.0.0 encapsulation frame-relay ! router rip network 3.0.0.0 network 160.0.0.0 ! line con 0 transport input none line aux 0 line vty 0 4 password cisco login ! end Router3#sh ip route Gateway of last resort is not set

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R 1.0.0.0/8 [120/1] via 160.0.0.1, 00:00:23, Serial0 R 2.0.0.0/8 [120/2] via 160.0.0.1, 00:00:23, Serial0 C 3.0.0.0/8 is directly connected, Loopback0 R 150.0.0.0/16 [120/1] via 160.0.0.1, 00:00:23, Serial0 C 160.0.0.0/8 is directly connected, Serial0 Router3#sh frame-relay pvc PVC Statistics for interface Serial0 (Frame Relay DTE) Active Inactive Deleted Static Local 1 0 0 0 Switched 0 0 0 0 Unused 0 0 0 0 DLCI = 400, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0 input pkts 141 output pkts 85 in bytes 17588 out bytes 8688 dropped pkts 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 35 out bcast bytes 3488 pvc create time 01:17:02, last time pvc status changed 00:24:03 Router3#sh frame-relay map Serial0 (up): ip 160.0.0.1 dlci 400(0x190,0x6400), dynamic, broadcast,, status defined, active