Overview
The Routing Information Protocol (RIP) is a distance-vector, interior gateway (IGP) routing protocol used by routers to exchange routing information. RIP uses the hop count as a routing metric. RIP prevents routing loops by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops allowed for RIP is 15. This hop limit, however, also limits the size of networks that RIP can support. RIP version 2 (RIPv2) was developed due to the deficiencies of the original RIP. It is usually used on small networks because it is very simple to configure and maintain but lacks some advanced features of other routing protocols like OSPF or EIGRP.
RIP Versions
There are two versions of RIP, version 1 and version 2. Both versions are distance vector routing protocols, and they use the number of hops or hop count as a routing metric. Both have an administrative distance of 120.
RIPv2 is an enhancement to the original RIP protocol developed in 1994.
RIPv2 is a classless routing protocol and it is capable of advertising subnet mask information and uses multicast to send routing updates.
RIPv1 is a classful routing protocol so it doesn’t advertise subnet masks and uses broadcast for updates. Version 2 is backwards compatible with version 1.
RIPv2 sends the entire routing table every 30 seconds, which can consume a lot of bandwidth, leading to slow convergence. RIPv2 also uses the multicast address of 224.0.0.9 to send routing updates, reducing network traffic and it supports authentication and triggered updates (updates that are sent when a change in the network occurs).
Although RIPv2 is more efficient than RIPv1, it is not deemed suitable for larger, more complex networks. It simply gives you more flexibility on smaller networks.
Routing Metric
RIPv2 uses the same routing metric as RIPv1, hop count. Hop count is the number of routers between a source and destination. RIPv2 also has the same hop count limit as RIPv1. If a route has more than 15 hops, the route will be discarded as invalid.
Routing Updates
Updates with RIPv2 are sent via multicasts and not broadcasts like the original RIP protocol. The multicasts are sent using a multicast address of 224.0.0.9. This helps prevent RIP routing table advertisements from being processed by every system on the network. Only systems that listen on the multicast address of 224.0.0.9 will process the updates.
RIPv2 can also be configured to do classless routing. When configured for classless routing, RIPv2 will transmit submit masks when it sends routing updates. This allows for the use of subnetting and non-contiguous networks.
RIPv2 allows for authentication to be required for updates. When authentication is enabled, each router is configured with the RIP update password. The password sent with the RIP update must match the password configured on the destination router. If the passwords do not match, then the receiving router will not process the update.
Note
The passwords sent with RIPv2 updates are sent in clear text. You can configure your router to use a Message Digest 5 (MD5) algorithm to secure the password.
Configuring RIPv2
RIP is one of the easiest protocols to configure. This is why it’s one of the most widely used. With just a few simple steps, you can have your routers configured to process RIP routing information. First, you start off by enabling RIPv2 on the router. Then, you must specify what networks you want to enable for RIPv2. These are the networks that will be tracked via the RIPv2 protocol.
Configuring RIPv2 on a Cisco Router
In this step-by-step exercise, we will configure RIPv2 routing on our router and enable it for network 192.168.1.0.
- Enter Privileged Exec mode with the enable command. Enter the enable password if you have one configured.
- Enter Global Configuration mode with the config t command.
- To enable RIPv2 and enter RIP configuration mode, type “router rip“
- Now enter network 192.168.1.0 to enable RIP for that network. You do not need to enter a subnet mask because RIP by default is classful and the default subnet mask is assumed.
You router is now configured to run the RIPv2 protocol, and RIP routing has been set for network 192.168.1.0.