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Distance vector routing
RIP
IGRP
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Distance Vector Updates
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Problem: Routing Loops
Routing loops can occur when inconsistent routingtables are not updated due to slow convergence in achanging network.
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Problem: Counting to Infinity
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Solution: Defining a Maximum forInfinity
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Solution: Split Horizon
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Solution: Route Poisoning
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Solution: Triggered Updates
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Solution: Holddown Timers
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RIP Routing Process
Open standard version of RIP has evolved over the years from a Classful
Routing Protocol, RIP Version 1 (RIP v1), to a Classless Routing Protocol,
RIP Version 2 (RIP v2). RIP v2 enhancements include:
Ability to carry additional packet routing information.
Authentication mechanism to secure table updates.
Supports variable length subnet masking (VLSM).
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Configuring RIP
router rip
Network X.y.z.w
IP RIP triggered
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Configuring RIP (Contd)
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Using the ip classless Command
Destination network and Router A Fa0/1 and Fa0/2 are in the same IP major
network
A B
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RIP Configuration Issues
To avoid routing loops and counting to infinity, RIPuses the following:
Defining infinity (Route marked as unreachable)
Split horizon (Prevent reverse route)
Route poisoning & poison reverse
Triggered updates (Speed up Convergence)Hold-down timers
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The show ip protocols Command
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The show ip route Command
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Troubleshooting RIP Update Issues
debug ip rip
show ip protocols
show ip route rip
show ip interface
Show running-config
ping
traceroute
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Preventing Routing Updates throughan Interface
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RIP V2 Overview
All of the operational procedures, timers, and stability functions ofRIP v1 remain the same in RIP v2, with the exception of thebroadcast updates
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Basic RIP V2 Configuration
When RIP is first enabled on a Cisco router, the router listens for version1 and 2 updates but sends only version 1. To take advantage of version 2features, it is necessary to turn off version 1 support and enable version 2updates with the following command:
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Compatibility with RIP V1
RFC 1723 defines a compatibility switch with four settings,
which allows versions 1 and 2 to interoperate:
1. RIP v1, in which only RIP v1 messages are transmitted
2. RIP v1 Compatibility, which causes RIP v2 to broadcast its
messages instead of multicast them so that RIP v1 may
receive them
3. RIP v2, in which RIP v2 messages are multicast to
destination address 224.0.0.9
4. None, in which no updates are sent
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Compatibility with RIP V1(Contd)
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IGRP Features
By default, the IGRP routing protocol uses bandwidth and delay as metrics.
Additionally, IGRP can be configured to use a combination of variables to
determine a composite metric.
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IGRP Commands
Using router igrp and networkcommands to enable IGRP
Enabling IGRP on an IP-addressed
network
Monitoring IP packet flow using the showip protocol command
The show ip interfaces command
The show ip route command
The debug ip rip command
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IGRP Metrics
Bandwidth The lowest bandwidth valuein the path
Delay The cumulative interface delayalong the path
Reliability The reliability on the linktowards the destination as determined by
the exchange of keepalives Load The load on a link towards the
destination based on bits per second
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IGRP Stability Features
Holddowns, Split horizons, & Poison-reverseupdates
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Configuring IGRP
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Migrating RIP to IGRP
1. Verify existing routing protocol (RIP) onthe routers to be converted.
2. Configure IGRP on RouterA and RouterB
3. Entershow ip protocolson RouterAand RouterB
4. Entershow ip route on RouterA andRouterB
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Verifying IGRP Configuration
Some commands for checking IGRPconfiguration are as follows:
show interface interface
show running-config
show running-config interfaceinterface
show running-config | begin interface
interface
show running-config | begin igrp
show ip protocols
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Troubleshooting IGRP
The following commands are useful whentroubleshooting IGRP:
show ip protocols {summary}show ip route
debug ip igrp
debug ip igrp transactions
ping
traceroute