Review of Chapter 4

IST 228\Ch5\IP Routing 1


Review of Chapter 4• Start the router simulator. You will see the prompt

"Router>". This is the user mode prompt.Change the name of the router to Router1.

• Set the enable password to “en123”.• Set the secret password to “secret123”.• Try the passwords.• Set virtual terminal password to “vty123” for the virtual

terminal 0-4Router1#config terminalRouter1(config)#line vty 0 4 Router1(config-line)#loginRouter1(config-line)#password vty123Router1(config-line)#exit

• Set console 0 password to “con123”Router1(config-line)#line console 0

• Now remove the passwords Router1(config)#no enable password en123


• Assign IP address for the Ethernet 0 interface.• Assign IP address for the Serial 0 interface.• Set the bandwidth of the Serial 0 interface to 56Kps.

Router1(config-if)#bandwidth 56• Set the bandwidth of the Serial 0 interface to 56Kps.

Router1(config-if)#clock rate 56000• Type “exit” to leave the serial interface and type “ctrl-z” to

leave configuration mode.• Show the configuration of Ethernet 0, Serial 0• Show the running configuration of Router1Backing up your configuration to a TFTP server

Router1#copy running-config tftp• Type “172.10.0.10” for the TFTP host.• Type “Router1” to name the destination file.

Router1#copy tftp running-config• Type “172.10.0.10” for the TFTP host.• Type “Router1” for the configuration file name.


IP Routing

• Nonroutable Protocols: – All communication occur on the one local net

segment– Network source and destination infromation is

not needed.– NetBEUI (NetBIOS Enhanced User Interface).

• Routed Protocols:– Have packet headers with Network Layer

address.– TCP/IP, Internetwork Packet Exchange/Squence

Packet Exchange.– Every device must configured with a unique IP or

IPX address.


IP Routing • Routers forward packets by looking the routing

table and discovering how to get remote networks.• A configured router have only information about

directly connected networks. – What happens a router receives a packet with a network

not listed in the routing table?

Routing table for RouterC


Different Types of Routing

• Static• Default• Dynamic


Static Routing•An administrator manually adds routes in each router’s table. •Benefits:

– No overhead on the router CPU– No bandwidth usage between routers– Security

•Disadvantages:– It is not feasible in large networks– Difficult to update– Administrators must know networking very well

ip route [destination_network] [mask] [next-hop_address or exit interface] [administrative_distance] [permanent]


Setting a Static Routing TableEstablishing routes:Router1# show ip route:Router1(config)# ip route 192.168.10.0 255.255.255.0

210.16.54.1This command establishes an IP route to network 192.168.20Add all other required routes in the routing tableType “crtl-Z” to exit from configuration mode. Check the status of the routing table using show ip route

Removing routes:Router1(config)# no ip route 192.168.10.0

255.255.255.0 210.16.54.1

Verifying:Router1# ping 192.168.10.50


Default Routing• Use to send packets with a remote

destination network not in the routing table to the next-hop router.

• You can only use default routing on stub networks-those with only one exit port out of the network.

RouterA(config)#ip route 0.0.0.0 0.0.0.0 192.168.12.1


Why use Default Routing?


Dynamic Routing• In dynamic routing, protocols are used to find and

update routing tables on routers.• A routing protocol defines the set of rules used by

a router when communicating between neighbor routers. – Routing Information Protocol (RIP)– Interior Gateway Routing Protocol (IGRP)– Enhanced Interior Gateway Routing Protocol (EIGRP)

• Types of routing protocols– interior gateway protocols (IGPs)

• RIP, IGRP, EIGRP, OSPF– exterior gateway protocols (EGPs)

• Border Gateway Protocol (BGP)

• Types of IGPs– Distance Vector (RIP, IGRP)– Link State (OSPF)– Hybrid (EIGRP)


Dynamic Routing Basics

• Hop count is the number of routers a packet must pass through to reach a particular network.

• An autonomous system (AS) is a group of routers under the control of a single administration, sharing the same routing table information.

• Administrative Distance is used to rate trustworthiness of routing information, 0 being the most trusted and the 255 least trusted.


Distance-Vector Routing Protocols• Each router broadcasts its entire routing

table to neighbor routers at predetermined intervals (30 to 90 seconds).

• Called routing by rumor


RIP Pinhole Congestion• Two updates list the same remote network?• Two updates list the same remote network and have the

same AD?• Two updates list the same remote network and have the

same AD and hop count?


Router Convergence

Start Up

Converged


Problems in Distance-Vector Routing• It takes up CPU process and link bandwidth.• If a network outage happens, slow converge

of distance-vector routing protocols can cause inconsistent routing tables.

• routing loops (counting-to-infinity).


Solutions

• Maximum Hop Count• Split Horizon• Route positioning• Holddowns


Routing Information Protocol (RIP)• a true distance-vector protocol• sends complete routing table out all

interfaces every 30 sec.• uses only hop count to determine the best

way.• has maximum allowable hop count of 15• is inefficient on large networks• uses three different timers

– route update timer– route invalid timer– flush timer


Setting up for Dynamic Routing• Configure your interfaces (see the next page)• Make sure that other routers in your network use

the same routing protocol (RIP or IGRP).Lab_A(config)# router rip

Lab_A(config-router)#network 201.100.11.0

^Z

• Check your settings with show ip route• Use ping to verify configuration and connectivity

of the network devices. • You can use passive-interface serial 0 to

stop RIP updates from being propagated out serial interface 0, but it can still receive RIP updates.


Example for RIP configuration


Interior Gateway Routing Protocol (IGRP)• Cisco-proprietary distance-vector routing

protocol that can work only with Cisco routers.

• maximum hop count of 255 (100 default)• can use bandwidth and delay of lines in

order to choose the best route.• Timers to control the performance

– update timers – invalid timers– holddown timers– flush


Commands to verify your configuration

Commands Meaning

show ip route shows you the routing protocols configured on your router and routing table

show protocols displays all routed protocols and the interfaces on which they are enabled.

show ip protocols shows the routing protocols with all timing associated with them

debug ip rip displays routing updates in the console session as they are sent and received.

debug ip igrp events displays a summary of the IGRP routing information running on the network

debug ip igrp transactions displays the message request from neighbor routers asking for updates.

undebug all turns all debugging off

show running-config shows the configuration currently running on the router


Commands for configuration routing

Commands Meaning

R(config)#router rip Turns on RIP routing on a router

R(config)#router igrp [AS number] Turns on IGRP routing on a router

R(config)#network [network IP] Identifies networks that routing table will be advertised by RIP and IGRP

R(config)#ip route [IP] [mask] [interface IP]

Creates static and default routes on a router

R(config)#ip route [IP] [mask] [interface IP]

Removes static and default routes

R(config)#ip classes Tells a router to forward packets to a default route when the destination network is not in the routing table


Commands to configure dynamic

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Review of Chapter 4

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