RIP - RIP V1 - RIP V2

RIP

The Routing Information Protocol (RIP) is one of the Internet's first widely used routing protocol. It is still useful in local and medium area networks.

RIP is classified as a distance-vector routing protocol, which employs the hop count as a routing metric, the maximum number of hops allowed for RIP is 15. A hop count of 16 is considered an infinite distance viewing such distance as unreachable and undesirable route in it routing process. This hop count limits the size of network that RIP operates.

RIP operates a hold down timer of 180 seconds, transmits full updates every 30 seconds.

RIP implements the hold down, split horizon, route poisoning mechanisms to prevent incorrect routing information from being propagated. These and many more are some of the stability features of RIP.

RIPv1

One of the deficiency of RIP (RIPv1) is the inability to propagate periodic routing updates of subnet information, and also does not support variable length subnet masks (VLSM).

RIPv1 Characteristics

* A classful, Distance Vector (DV) routing protocol

* Routing Metric - Hop count

* Routes with hop count > 15 are unreachable

* Updates are broadcast every 30 seconds

* Default administrative distance is 120

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

Like RIPv1, RIPv2 is a distance vector routing protocol. Both versions of RIP share the following features and limitations:

• Use of hold down and other timers to help prevent routing loops.
• Use of split horizon or split horizon with poison reverse to also help prevent routing loops.
• Use of triggered updates when there is a change in the topology for faster convergence.
• Maximum hop count limit of 15 hops, with the hop count of 16 signifying an unreachable network.