RIP

Overview

By default, RIPv2 sends updates to the multicast address 224.0.0.9. However, we can force RIPv2 to work with broadcasts instead like RIPv1 with the following command.

R1(config-if)# ip rip v2-broadcast

RIP version can be set on interface level.

R1(config-if)# ip rip send version [1|2]
R1(config-if)# ip rip receive version [1|2]

Timer

There are 4 types of timer here.

Update(30s)
InvalidAfter(180s)
Holddown(180s)
FlushAfter(240s)

A route becomes invalid after it is not received for 180s and holddown timer starts. Holddown mode runs for 180s and the route is considered as possibly down in this state. However, since flush timer is 240s by default, the holddown timer will keep only 60s.

R2#show ip route rip

      1.0.0.0/24 is subnetted, 1 subnets
R        1.1.1.0/24 is possibly down,

router rip
timers basic <update> <invalid> <hold> <flush> <sleep>

Manual Route Summarization

R1(config-if)# ip summary-address rip 1.0.0.0 255.0.0.0

Distribute List

R1(config)# router rip 
R1(config-router)# distribute-list 1 out serial 0/1

If an extended ACL is used here, the route is put in the destination part and the source part is the advertising router or 0.0.0.0 for any.

Redistribution

When redistributing into RIP, make sure you set the metric.

Option 1

router rip
  redistribute eigrp 1 metric 3

Option 2

router rip
  default-metric 3
  redistribute eigrp 1

When redistributing into RIP from another protocol, the network of the directly connected interface that the protocol being redistributed is running on will be redistributed automatically.

Default Route Advertisement

There are three ways to advertise a default-route into RIP

router rip
  default-information originate [route-map <route-map>]

Default route is always advertised by default with this command. The match command in the route-map here matches the device's ip table, it checks whether there is a route matches the ip.

ip route 0.0.0.0 0.0.0.0 100.100.100.1
router rip
  redistribute static metric 3

ip defaulot-network

Authentication

R1(config-if)# ip rip authentication mode [text | md5]
R1(config-if)# ip rip authentication key-chain KC

Miscellaneous

Update Source Validation

By default, RIP checks the source IP address of incoming updates. If we want to disable it, use the following command.

R1(config-router)# no validate update-source

Triggered Updates

RIP barfs out all the information it has every update time(30s by default). But triggered update can be enabled using the following command.

(config-if)# ip rip triggered

This is only available on serial interfaces.

Interpacket Delay

(config-router)# output-delay <delay>

RIP

RIP