13 - operating cisco routers

13 - Operating Cisco Routers

By Muhammad Asghar Khan

Reference: CCENT/CCNA ICND1 Official Exam Certification Guide By Wendell Odom

www.asghars.blogspot.com2

Agenda Differences between Switches & Routers Installing Cisco Routers

Installing Enterprise Routers Installing Internet Access Routers

Comparisons Between the Switch CLI and Router CLI Cisco Router Configuration

Initial Configuration (Setup Mode) Router Interfaces Interface Status Codes Router Interface IP Addresses

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Agenda Clock Rate & Bandwidth of Serial Interfaces Auxiliary (Aux) Port

Upgrading Cisco IOS Cisco IOS Boot Process

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Differences between Switches & Routers Switches forward Ethernet frames by comparing the frame’s

destination MAC address to the switch’s MAC address table, whereas routers forward packets by comparing the destination IP address to the router’s IP routing table

Ethernet switches typically have only one or more types of Ethernet interfaces, whereas routers have Ethernet interfaces, serial WAN interfaces, and other interfaces with which to connect via cable and digital subscriber line (DSL) to the Internet

Switches operate on data link layer (L2) while routers provide the main feature of the network layer (L3)

Even though their core purposes differ, Cisco routers and switches use the same CLI

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Installing Cisco Routers Installing Enterprise Routers

A typical enterprise network has a few centralized sites as well as lots of smaller remote sites

To support devices at each site (the computers, IP phones, printers, and other devices), the network includes at least one LAN switch at each site

Each site has a router, which connects to the LAN switch and to some WAN link

Figure on next slide shows the detailed diagram of part of an enterprise network

The LAN connections all use UTP straight-through cabling pinouts, except for the UTP cable between the two switches, which is a crossover cable

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Installing Cisco Routers The WAN cable installed by the telco typically has an RJ-48

connector, which is the same size and shape as an RJ-45 connector

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Installing Cisco Routers Cisco has several router product series called Integrated

Services Routers (ISR) In ISR many functions are integrated into a single device

like Cisco offers single devices that act as both router and switch

The Cisco 1841 ISR provides the internal CSU/DSU unit

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Installing Cisco Routers Physical Installation

1. Connect any LAN cables to the LAN ports2. If using an external CSU/DSU, connect the router’s serial

interface to the CSU/DSU, and the CSU/DSU to the line from the telco

3. If using an internal CSU/DSU, connect the router’s serial interface to the line from the telco

4. Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router

5. Connect a power cable from a power outlet to the power port on the router

6. Turn on the router

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Installing Cisco Routers Installing Internet Access Routers

Routers play a key role in Small Office/Home Office (SOHO) networks, connecting the LAN-attached end-user devices to a high-speed Internet access service

A SOHO Installation with a Separate Switch, Router, and Cable Modem Figure on next slide shows an example of the devices and

cables used in a SOHO network to connect to the Internet using cable TV (CATV) as the high-speed Internet service

The end-user PCs still connect to a switch, and the switch still connects to a router’s Ethernet interface

The voice adapter converts analog voice to IP

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Installing Cisco Routers Cable Modems /DSL Modems convert electrical signals

between an Ethernet cable and either CATV or DSL

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Installing Cisco Routers Physical Installation

1. Connect a UTP straight-through cable from the router to the switch

2. Connect a UTP straight-through cable from the router to the cable modem

3. Connect the router’s console port to a PC (using a rollover cable), as needed, to configure the router

4. Connect a power cable from a power outlet to the power port on the router

5. Turn on the router

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Installing Cisco Routers A SOHO Installation with an Integrated Switch, Router,

and DSL Modem SOHO devices include functions like router, switch, cable

or DSL modem, voice adapter, wireless AP and hardware enabled encryption

SOHO Internet connectiontoday probably looks morelike as shown below with anintegrated device

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Comparisons Between the Switch CLI and Router CLI The following configuration commands are the same on

both routers and switches: User and Enable (privileged) mode Configure terminal , end , and exit commands, and the

Ctrl-Z key sequence Configuration of console, Telnet, and enable secret

passwords Configuration of SSH encryption keys and

username/password login credentials Configuration of the host name and interface description

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Comparisons Between the Switch CLI and Router CLI

Configuration of Ethernet interfaces that can negotiate speed, using the speed and duplex commands

Configuring an interface to be administratively disabled ( shutdown) and administratively enabled (no shutdown)

Navigation through different configuration mode contexts using commands like line console 0 and interface

CLI help, command editing, and command recall features The meaning and use of the startup-config (in NVRAM),

running-config (in RAM), and external servers (like TFTP), along with how to use the copy command to copy the configuration files and IOS images

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Comparisons Between the Switch CLI and Router CLI

The process of reaching setup mode either by reloading the router with an empty startup-config or by using the setup command

The following configuration commands are different in routers compared to switches:

The configuration of IP addresses differs in some ways The questions asked in setup mode differ Routers have an auxiliary (Aux) port, intended to be

connected to an external modem and phone line, to allow remote users to dial into the router, and access the CLI, by making a phone call

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Cisco Router Configuration Initial Configuration (Setup Mode)

The processes related to setup mode in routers follow the same rules as for switches

You can reach setup mode either by booting a router after erasing the startup-config file or by using the setup enable-mode EXEC command

Note, routers need to know the IP address and mask for each interface on which you want to configure IP, whereas switches have only one IP address

Example on next slide demonstrates the use of setup mode

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Cisco Router Configuration

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Cisco Router Configuration Router Interfaces

There are two general types of physical interfaces on routers: Ethernet interfaces and serial interfaces

Routers use numbers to distinguish between the different interfaces of the same type

The following example lists the interfaces in a router

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Cisco Router Configuration Interface Status Codes

The two interface status codes (Line Status; refers to the L1 status & Protocol Status; refers to the L2 status) on the interface must be in an “up” state

Four combinations of settings exist for the status codes when troubleshooting a network

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Router Interface IP Addresses Routers need an IP address on each interface If no IP address is configured, even if the interface is in an

up/up state, the router will not attempt to send and receive IP packets on the interface

Example on next slide shows a configuration of IP addresses on an interface

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Cisco Router Configuration Clock Rate & Bandwidth of Serial Interfaces

Ethernet interfaces use either a single speed or one of a few speeds that can be auto-negotiated

However, WAN links can run at a wide variety of speeds To deal with the wide range of speeds, routers physically

slave themselves to the speed as dictated by the CSU/DSU through a process called clocking

In effect, the CSU/DSU tells the router when to send the next bit over the cable, and when to receive the next bit, with the router just blindly reacting to the CSU/DSU for that timing

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Cisco Router Configuration Routers use two different interface configuration commands

that specify the speed of the WAN link connected to a serial interface, namely the clock rate and bandwidth interface subcommands

The clock rate command dictates the actual speed (in bps)used to transmit bits on a serial link, but only when the physical serial link is actually created with cabling in a lab

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Cisco Router Configuration The clock rate speed interface subcommand sets the rate

in bits per second on the router that has the DCE cable plugged into it

To find which router has the DCE cable in it, you can find out by using the show controllers command, which lists whether the attached cable is DCE or DTE

The second interface subcommand bandwidth tells IOS the speed (in kbps)of the link, in kilobits per second

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Cisco Router Configuration Note, the bandwidth setting does not change the speed

at which bits are sent and received on the link. Instead, the router uses it for documentation purposes, particularly; the EIGRP and OSPF routing protocols use the interface bandwidth settings to set their default metrics

Auxiliary (Aux) Port The Aux port is connected via a cable (RJ-45, 4 pair, with

straight-through pinouts) to an external analog modem The engineer uses a PC, terminal emulator, and modem to

call the remote router

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Cisco Router Configuration Aux ports can be configured beginning with the line aux 0

command to reach aux line configuration mode Cisco switches do not have an Aux port

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Upgrading Cisco IOS Routers and switches store IOS images in Flash memory Flash memory is rewriteable, permanent storage Additionally, the IOS image can be placed on an

external TFTP server, but external server is typically used for testing and not in production

The copy tftp flash command is used to copy the IOS image from external server to flash memory

During this process of copying the IOS image into Flash memory, the router asks for questions like IP of tftp server, the name of image file to be copied

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Upgrading Cisco IOS Example below demonstrate these steps

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Upgrading Cisco IOS Use the show flash command to verify the contents of

Flash memory

Once the new IOS has been copied into Flash, the router must be reloaded (rebooted) to use the new IOS image

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RAM

Cisco IOS Boot Process When a router first powers on, it follows four steps,

these steps are graphically depicted in the following figure

ROM

FlashTFTPROM

NVRAMTFTP

Console

Bootstrap

IOS Image

Running Config

File

POSTStartStep 2

Step 1

Step 3

Step 4

Performs a power-on self-test to verify that all components work properly

1

Router copies a bootstrap program from ROM into RAM, and runs the bootstrap program 2

bootstrap program decides which IOS image (from flash, tftp or rom) to load into RAM, and loads that OS

3

IOS finds the configuration file (from nvram, tftp or console) typically the startup-config file in NVRAM and loads it into RAM as the running-config

4

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Cisco IOS Boot Process Cisco routers can use a different OS to perform some

troubleshooting, to recover router passwords, and to copy new IOS files into Flash when Flash has been inadvertently erased or corrupted

In the more recent additions to the Cisco router product line (e.g., 1800 and 2800 series routers), Cisco routers use only one other OS, whereas older Cisco routers (e.g., 2500 series routers) actually had two different operating systems to perform different subsets of these same functions ROM Monitor (ROMMON) used in old and new routers Boot ROM(RxBoot, Boot Helper) only used in older routers

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Cisco IOS Boot Process A router chooses the OS to load based on the low-order

4 bits (boot field) in the configuration register and the details configured in any boot system global configuration commands found in the startup-config file

The configuration register is a special 16-bit number that can be set on any Cisco router

The command config-register value is used to change the value of configuration register

The 0x2100 causes the router to load the ROMMON OS instead of IOS

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Cisco IOS Boot Process The process to choose which OS to load, on more

modern routers that do not have an RxBoot OS, happens as follows: If boot field = 0, use the ROMMON OS If boot field = 1, load the first IOS file found in Flash

memory If boot field = 2-F:

Try each boot system command in the startup-config file, in order, until one works. If none of the boot system commands work, load the first IOS file found in Flash memory

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Cisco IOS Boot Process Following is the several examples of the boot system

commands: boot system flash; load first file boot system flash filename; load file with specified name boot system tftp filename 10.1.1.1; load file from tftp

server

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Cisco IOS Boot Process The show version

command supplies

a both the current

value of the

configuration

register and

the expected value

at the next reload

of the router

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13 - operating cisco routers

Documents

installing

upgrading

clock rate

ios file found

interface

routers serial

cisco router

routers console