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Routing Information Protocol version 2 (RIPv2)

Link to: RIPv2 Basics and to: How to Configure RIPv2.

RIPv2 is a classless, distance vector routing protocol as defined in RFC 1723. Because RIPv2 is a classless routing protocol, which means, it includes the subnet mask with the network addresses in the routing updates. As with other classless routing protocols, RIPv2 supports CIDR supernets, VLSM and discontiguous networks.

Due to the deficiencies of RIPv1, RIP version 2 (RIPv2) was developed sometime in 1993. It’s equipped with the ability to support subnet information and supports Classless Inter-Domain Routing (CIDR). A router that receives routing updates from multiple routers advertising the same classful summary route cannot determine which subnets belong to which summary route. This inability leads to unexpected results including misrouted packets.

However, with RIPv2 automatic summarization can be disabled with the no auto-summary command. Automatic summarization must be disabled to support discontiguous networks.

RIPv2 still maintains the hop count limit of 15 and incorporated a password authentication mechanism. However, passwords were transmitted in clear-text format, which were found insufficient for secure communications on the Internet.

The default version of RIP is version 1. The command version 2 is used to modify RIPv1 to RIPv2.

Use The show ip protocols command to view that RIP is now sending and receiving version 2 updates and whether or not automatic summarization is in effect.

RIPv2 is actually an enhancement of RIPv1's features and extensions rather than an entirely new protocol. Some of these enhanced features include:
  •Next-hop addresses included in the routing updates
  •Use of multicast addresses in sending updates
  •Authentication option available

RIPv2 Summary

The characteristics of RIPv2 follow:
  •Distance-vector protocol.
  •Uses UDP port 520.
  •Classless protocol (support for CIDR).
  •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
  •25 routes per RIP message (24 if you use authentication).
  •Supports authentication.
  •Subnet mask included in route entry.
  •Administrative distance for RIPv2 is 120.
  •Used in small, flat networks or at the edge of larger networks.
  •Uses holddown and other timers to help prevent routing loops.
  •Uses split horizon or split horizon with poison reverse to also help prevent routing loops.
  •Uses triggered updates when there is a change in the topology for faster convergence.