RIP

I'm at my favorite coffee house this evening getting RIPped! I had an amazing barista make a blended espresso...so good!

RIP the Routing Information Protocol

• is a Distance Vector routing protocol using Hop count as its metric, 15 hops maximum
• it will perform Equal Cost Multi Path, for up to 4 paths by default

RIPv1                                              * RIPv2

• is a legacy protocol                     * Both versions are still supported by Cisco
• does not support VLSM               * supports VLSM (subnetting)
• every 30 sec. broadcast updates  *uses multicast address 224.0.0.9
• no route authentication                *supports authentication

  note: RIPng (RIP next generation) supports IPv6 networks

RIPv2 Configuration
  R1(config)# router rip
  R1(config-router)# version 2
  R1(config-router)# network 10.0.0.0
      * the "network" here is classful (/8), so no need for a subnet mask
      * by default RIPv2 uses Auto-Summary along the classful boundary
         𛲡 ex 192.168.10.1/30 will be advertised at 192.168.10.0/24
         𛲡 ex  172.16.10.1/30  advertised at 172.16.0.0/16
  R1(config-router)# no auto-summary    (removes the above)

     * if summarization is needed you can manually define it
     * the summarized route is configured on the interface that should advertize the route
  R2(config-router)# interface f1/0
  R2(config-if)# Ip summary-address rip 10.0.0.0  255.255.0.0

  Handy commands:
     R1#show ip protocols   (this will show all routing protocols on the router)
     R1#show run | section rip  
     R1#show ip route
     R1#show ip rip database

Advanced concepts:
Passive interfaces in all other IGPs do not send out or listen for routing updates. And the network on these interfaces must be manually configured into the routing table to be shared with peer routers.
    RIPs passive interfaces do not send out updates but do listen to incoming updates from other RIP speaking neighbors. the router can receive updates on the passive interface and use them in the routing table. 
  R1(config)#router rip
  R1(config-router)# passive-interface loopback 0   (best practise)
  R1(config-router)#passive-interface fa2/0 (port connects to external company)

  Alternatively, make all ports on the router passive and then specify the interfaces that are not passive.
  R1(config)#router rip
  R1(config-router)# passive-interface default
  R1(config-router)#no passive-interface fa0/0
  R1(config-router)#no passive-interface fa1/0

Default Router Injection:  used to configure a default route on the router with the "internet connection" and force it to all other routers in the network.
  R4(config)#ip router 0.0.0.0 0.0.0.0 203.0.113.2  (standard static route)
  R4(config)#router rip
  R4(config-router)# default-information originate

RIP Default Timers

• Update: The router sends updates every 30 seconds.
• Invalid: After no updates for 180 seconds the route becomes invalid
• Hold Down: this timer is used to stabilize the network and starts when the invalid timer completes. During this timer, no new routes are accepted, even if they have better metrics
• Flush: 240 seconds from the last update the route is flushed.

• The timers can be changed to achieve faster convergences but if too short they can introduce instability. All routers in the network must have the same timers
•   R1(config)#router rip
•   R1(config-router)#timers basic 10 90 90 120