ccna exp2 - chapter02 - static routing

8/3/2019 CCNA Exp2 - Chapter02 - Static Routing

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Chapter 2-Static Routing

CCNA Exploration 4.0


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Objectives

Define the general role a router plays in networks. Describe the directly connected networks, different router

interfaces

Examine directly connected networks in the routing tableand use the CDP protocol

Describe static routes with exit interfaces Describe summary and default route Examine how packets get forwarded when using static

routes Identify how to manage and troubleshoot static routes


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Role of the Router

The router is a special-purpose computer that plays a key role inthe operation of any data network. Routers are primarilyresponsible for interconnecting networks by:

Determining the best path to send packets.

Forwarding packets toward their destination.


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Introducing the topology

Topology Lab Three 1800 series routers connected via WAN links.

Each router connected to a LAN represented by a switch anda PC.


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Cable for LAN/WAN interfaces


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Examining Router Interfaces

Examining Router Interfaces show ip route command used to view routing table

show interfaces command used to show status of an interface

show ip Interface brief command used to show a portion of theinterface information

show running-config command used to show configuration file inRAM


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Configuring an Ethernet Interface

Configuring an Ethernet interface By default all serial and Ethernet interfaces are admintrative down.

To enable an interface use the no shutdown command.


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Logging Synchronous Command

In order to keep the unsolicited output separate from your input,enter line configuration mode for the consoled port and add thelogging synchronous command.



Configuring a Serial Interfaces

Configuring a Serial interface Enter interface configuration mode

Enter in the ip address and subnet mask

Enter in the clock rate(DCE) and no shut down command

Example:

R1(config)#interface serial 0/0 R1(config-if)#ip address 172.16.2.1 255.255.255.0

R1(config-if)#clock rate 64000

R1(config-if)#no shutdown



Verifying Changes to the Routing Table

The routing table consists of a list of "known" network addressesthese addresses that are directly connected, configuredstatically, and learned dynamically.



Verifying Changes to the Routing Table

Observing Routes as They are Added to the Routing Table debug ip routing command will let us see any changes that

the router performs when adding or removing routes.



Devices on Directly Connected Networks

When a router only has its interfaces configured, and the routingtable contains the directly connected networks but no otherroutes, only devices on those directly connected networks arereachable.



Devices on Directly Connected Networks



Cisco Discovery Protocol (CDP)

Network discovery with CDP

CDP is an information-gathering tool used by network administrators toget information about directly connected Cisco devices.

CDP is a proprietary tool that enables you to access a summary ofprotocol and address information about Cisco devices that are directlyconnected.

These advertisements contain information such as the types of devicesthat are connected, the router interfaces they are connected to, theinterfaces used to make the connections, and the model numbers ofthe devices.

Concept of neighbors

2 types of neighbors

Layer 3 neighbors.

Layer 2 neighbors.



Cisco Discovery Protocol (CDP)

CDP Operation

CDP runs at the Data Link layer connecting the physical media to theupper-layer protocols (ULPs).

Cisco network devices, such as routers that support different Networklayer protocols (for example, IP and Novell IPX), can learn about eachother

CDP provides the following information about each CDP neighbordevice:

Device identifiers

Address list

Port identifier Capabilities list

Platform



Default Setting

Feature Default Setting

CDP global state Enabled

CDP interface state Enabled

CDP holdtime (packet holdtime inseconds)

180

CDP timer (packets sent every x seconds) 60



Using CDP for Network Discovery

The information gathered by the CDP protocol can be examinedwith the show cdp neighbors command.




Field Definition

Device ID The name of the neighbor device and either theMAC address or the serial number of thisdevice.

Local Intrfce The protocol being used by the connectivitymedia.

Holdtme The remaining amount of time (in seconds) thecurrent device will hold the CDP advertisement

from a sending router before discarding it.




Capability(CapabilityCodes)

Capability (type of routing device) of the listedneighboring device.The capability types that can be discovered are:RRouterTTransparent bridge

BSource-routing bridgeSSwitchHHostI device is using IGMPrRepeater

Platform The product number of the device.

Port ID The protocol and port number of the device.




To disable CDP on aspecific interfaceafter it has beenenabled, use the noCDP enable

command in interfaceconfiguration mode.



CDP Commands


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CDP Commands


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STATIC ROUTING



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Purpose and Command Syntax of ip route

Static routes are commonly used when routing from a network toa stub network.

A stub network is a network accessed by a single route.


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ip route command

RTR(config)# ip routeprefix mask {address |

interface} [distance] [tag tag] [permanent]

prefix IP route prefix for the destination.

mask Prefix mask for the destination.

address IP address of the next hop that can be used to reach

that network.

interface Network interface to use (exit-interface)

distance (Optional) An administrative distance.

tag tag (Optional) Tag value that can be used as a "match" value

for controlling redistribution via route maps. (CCNP Advanced Routing)

Permanent (Optional) Specifies that the route will not be removed,even if the interface shuts down. (CCNP Advanced Routing)


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Configuring Static Routes

Installing a Static Route in the Routing Table


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Configuring Static Routes

Configuring Routes to Two More Remote Networks


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Routing Table Principles and Static Routes


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Routing Table Principles and Static Routes

Applying the Principles


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Resolving to an Exit Interface


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Resolving to an Exit Interface

Exit Interface is Down


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Configuring a Static Route with an Exit Interface

Static routes can be configured with an exit interface, which

allows the routing table to resolve the exit interface in a singlesearch instead of two searches.

d


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ip route command

RTR(config)# ip routeprefix mask {address |

interface} [distance] [tag tag] [permanent]

prefix IP route prefix for the destination.

mask Prefix mask for the destination.

address IP address of the next hop that can be used to reach

that network. interface Network interface to use (exit-interface)

distance (Optional) An administrative distance.

tag tag (Optional) Tag value that can be used as a "match" value

for controlling redistribution via route maps. (CCNP Advanced Routing) Permanent (Optional) Specifies that the route will not be removed,

even if the interface shuts down. (CCNP Advanced Routing)


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Configuring a Static Route with an Exit Interface

Static Route and an Exit Interface


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Modifying Static Routes

There are times when a previously configured static route needs to be

modified: The destination network no longer exists, and therefore the static route

should be deleted.

There is a change in the topology, and either the intermediate addressor the exit interface has to be changed.

V if i h S i R C fi i


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Verifying the Static Route Configuration

Verifying the Static Route Configuration

Use the following commands Step 1 show running-config.

Step 2 verify static route has been entered correctly.

Step 3 show ip route.

Step 4 verify route was configured in routing table. Step 5 issue ping command to verify packets can reach

destination and that Return path is working.

S i R i h E h I f


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Static Routes with Ethernet Interfaces

Ethernet interfaces and ARP. If a static route is configured on an

Ethernet link If the packet is sent to the next-hop router then the destination MAC

address will be the address of the next hops Ethernet interface

This is found by the router consulting the ARP table. If an entryisnt found then an ARP request will be sent out

S i R i h E h I f


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Static Routes with Ethernet Interfaces

Static routes and Ethernet exit interfaces

With Ethernet networks, there may be many different devices sharingthe same multi-access network, including hosts and even multiplerouters. Thefore, router does not know the next-hop IP address andtherefore it cannot determine the destination MAC address for theEthernet frame.

S St ti R t


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Summary Static Routes

Route Summarization

Summarizing Routes to Reduce the Size of the Routing Table Multiple static routes can be summarized into a single static route if:

The destination networks can be summarized into a single networkaddress, and

The multiple static routes all use the same exit-interface or next-hop IP address

S St ti R t


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Summary Static Routes

Configuring a Summary Route

Configuring a summaryroute

Step 1: Delete thecurrent static route

Step 2: Configure thesummary static route

Step 3: Verify the newstatic route

D f lt St ti R t


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Default Static Route

A default static route is a route that will match all packets. Default static

routes are used: When no other routes in the routing table match the packet's

destination IP address. In other words, when a more specific matchdoes not exist. A common use is when connecting a company'sedge router to the ISP network.

When a router has only one other router to which it is connected.This condition is known as a stub router.

Using command: ip route 0.0.0.0 0.0.0.0 {exit Interface, IPNextHop}

D f lt St ti R t


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Default Static Route

Verifying a Default Static Route

St ti R t d P k t F di


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Static Routes and Packet Forwarding


St ti R t d P k t F di


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Troubleshooting a Missing Route


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Tools that can be used to isolate routing problems include: Ping tests end to end connectivity

Traceroute used to discover all of the hops (routers) along thepath between 2 points

Show IP route used to display routing table & ascertain forwardingprocess

Show ip interface brief- used to show status of router interfaces

Show cdp neighbors detail used to gather configurationinformation about directly connected neighbors

Summary


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Summary

Routers

Operate at layer 3 Functions include best path selection & forwarding

packets Connecting Networks

WANs

Serial cables are connected to router serial ports. In the lab environment clock rates must be configured for

DCE

LANs Straight through cables or cross over cables are used to

connect to fastethernet port. (The type of cable useddepends on what devices are being connected)

Cisco Discovery Protocol A layer 2 proprietary protocol Used to discover information about directly connected

Cisco devices

Summary


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Summary

Static Routes

This is a manually configured path that specifies how therouter will get to a certain point using a certain path.

Summary static routes This is several static routes that have been condensed into a

single static route.

Default route It is the route packets use if there is no other possible matchfor their destination in the routing table.

Forwarding of packets when static route are used Zinins 3 routing principles describe how packets are

forwarded

Troubleshooting static routes may require some of thefollowing commands: Ping Traceroute Show IP route Show ip interface brief Show cdp neighbors detail


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ccna exp2 - chapter02 - static routing

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