RIPv2 Summary

The characteristics of RIPv2 follow:
- Distance-vector protocol.
- Use UDP port 520.
- Makes Automatic summarization on network Class boundary.
- Classless protocol (supports VLSMs).
- Have the power to shut the Auto-summarization And make a configured manual Summarization.
- Supports VLSMs.
- Metric is router hop count.
- Maximum hop count is 15; infinite (unreachable) routes have a metric of 16.
- Periodic route updates sent every 30 seconds to multicast address 224.0.0.9.
- 25 routes per RIP message (24 if authentication is used).
- Invalid route marked after 180 sec.
- Flush timer is 280 sec.
- Hold-down timer 180 sec.
- Supports authentication.
- Implements split horizon with poison reverse.
- Implements triggered updates.
- Subnet mask included in route entry.
- Administrative distance for RIPv2 is 120.
- Used in small, flat networks or at the edge of larger networks.
RIPv2 Convergence
The steps for RIPv2 convergence are as follows:
1- When the local router sees a connected route disappear, it sends a
Flash update and removes the route entry from its table. This is
Called a triggered update with poison reverse.

2- The receiving routers send a Flash update and put the affected route
in holddown.

3- The originating router queries its neighbor (DC) for alternative routes.
If the neighbor has an alternative route, it is sent; otherwise, the
Poisoned route is sent.

4- The originating router installs the best alternative route that it
hears because it has purged the original routes, and Send the new updates in
its periodic routing update timer (30 sec).

5- Routers that are in holddown ignore only the alternative route.

6- When the other routers emerge from holddown, they will accept
the alternative route.

7- Convergence takes the time for detection, plus holddown, plus the
number of routing updates (equal to the hop-count diameter of the network).
This could take a long time.

RIP v2 Configuration

config)# router rip
conf-router)# version 2
conf-router)# no auto-summary
conf-router)# network < classfull Net ID>

conf-router)#passive-interface

conf-router)#maximum –paths (Up to 6 Links for load sharing on a R.B basis, Over equal metric paths default =is 4 paths)

conf-if)# no ip split-horizon (Disables it from a specific interface)
c
onf-router)#distance (Define an administrative distance, default =120)

conf-router)# timers basic < update - invalid –holdown –flush – sleep > (Adjust timers in sec , Sleeptime is a timer used to specify a period, in milliseconds, to delay a regular routing update after receiving a triggered update.)

conf-router)# neighbor < ip add> (Because RIP is a broadcast protocol you may configure RIP to exchange routing information in a Point-Point non-broadcast network such as Frame Relay. In this type of network, RIP must be informed of neighbor RIP routers, Also When it is used in combination with the passive-interface cmd, routing information can be Only exchanged between the router and this nei Ex. Unix server on a LAN )

conf-router)#validate-update-source (This command is applicable only to RIP and IGRP. The software ensures that the source IP address of incoming routing updates is on the same IP network as one of the addresses defined for the receiving interface. Disabling split horizon on the incoming interface will also cause the system to perform this validation check. For unnumbered IP interfaces (interfaces configured as IP unnumbered), no checking is performed. )

conf-router)# no auto-summary
conf-if )# ip summary-address rip < Net ID + mask>


Show Commands

# sh ip route
# sh ip route rip
# sh ip route < Net ID >
# sh ip rip database
# sh ip protocols

#debug ip rip
#debug ip rip events
# no debug all


Hope this might be usefull