Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is a dynamic routing protocol defines a way for routers, which connect different networks using the Internet Protocol (IP), to share information about how to route traffic among these different networks. The routing information protocol (RIP) uses hop count as a routing metric to find the best path between the source and the destination network. Hop count is the number of routers along the path between the source and destination network. The path with the lowest hop count between source and destination considered as the best path and therefore placed in the routing table.

RIP exchange routing updates periodically in the shape of the broadcast after every 30 seconds. Each time it broadcast the entire routing table to its closest neighbors routers. The neighbors are the routers that are connected directly to this router. The neighbors will pass the information on to their nearest neighbors, and so on The routers always trust on routing information received from neighbor routers. This is also known as routing on rumours. There are three versions of routing information protocol – RIP Version 1RIP Version 2, and RIPng.

In case of router crash or a network connection is disruption; the network discovers this because that router will not send an update to its neighbors and If the discontinued remain for 180 seconds, RIP router will drop that route.

RIP also prevents routing loops by limiting the number of hops allowed in a path from source and destination. The maximum hop count allowed for RIP is 15 and hop count of 16 considered as network unreachable. It is a distance-vector routing protocol which has AD value 120; and works on the application layer of the OSI model. RIP uses port number 520.

The RIP cannot scale very large and complex networks. The RIP pushes its whole routing table every 30 seconds as a result, it cannot converge quickly. RIP uses only due to its simplicity.  Mostly RIP not uses in modern networking; it is only the foundation for networking student to understand routing.

RIP Configuration

This article explains how to configure RIP Routing protocol step by step in detail. RIP is a Distance Vector routing protocol. Learn how to enable router RIP configuration mode and configure Routing Information Protocol routing in Cisco router with the example in packet tracer.

Routing Information Protocol Configuration Mode

Routing Information Protocol

The figure above shows the reference topology including its IP addresses. In the topology, all routers have configured with basic management features and all interfaces are configured and enabled. There are no dynamic and static routes configured; therefore, we cannot access the routers remotely.  We can enable RIP protocol, using the router rip command, as shown below.

  • Router0(config)#router rip
  • Router0(config-router)#

The command provides access to the router configuration mode where the RIP routing settings are configured.

To eliminate and remove the RIP configuration, use the no router rip command in global configuration mode. Executing this command immediately stops the RIP process and erases all existing RIP configurations. To display and check the router mode command execute the question mark(?) command in router mode as shown in the figure below.

Routing Information Protocol (RIP) 4

Advertising Networks

After entering the RIP router configuration mode, it needs to know which local interfaces should use to communicate with other routers, as well as which locally connected networks it should advertise to those routers. To configure a RIP routing for a network, use the following command:

  • Router0(config-router)#network  <netwowrk address>

In the network-address enter the classful network address for each directly connected network. This command enables Routing Information Protocol on all interfaces that belong to a specific network and the associated interfaces now can also send and receive RIP update. The router can advertise the particular network in RIP routing update sending to other routers on every 30 seconds. If in the network-address parameter we enter the subnet, the router IOS automatically converts the classless network address to classful network address. Because RIPv1 is a classful routing protocol for IPv4.

For example, if we enter the network address 192.168.1.32 the IOS would automatically convert the network 192.168.1.0 in the running configuration file without displaying any error message, but instead corrects the input and enters the classful network address. Following is the route advertisement configuration of this topology

  • Router0 Route Advertisement

Routing Information Protocol (RIP) 5

  • Router1 Route Advertisement

The Router1 has five networks to advertise after configuring IP addresses to router interface following is the procedure to advertise its network.

Routing Information Protocol (RIP) 6

The remaining routers in the topology have one route each to advertise in this topology. We can advertise routes in the same way. The complete configuration can be view in the video.

Examining Default RIP Settings

To examine and show the default RIP setting use the show ip protocols command in privileged exec mode. The figure below illustrates the output of this command on Router0 of the reference topology:

The command should display the IPv4 routing protocol settings currently configured on the router. The most parameters displays in Figure above including the following:

  • The configured routing protocol is RIP
  • The timers values, for example, the next routing update, is sent by R1 in 21 seconds. Invalid after 180 seconds, hold down timing and flush timing
  • The version of RIP currently configured
  • Current route summarization state
  • Current paths and routing for the network.
  • The routing information source including administrative distance value currently configured.
  • This command is also useful to verify other routing protocols and their operation.

The other command showing and verifying the routing protocol is the show ip route command. The command should display the Routing Information Protocol routing table. We can also verify the Routing Information Protocol configuration from show startup-config and show running-config

Enabling RIPv2

When a Routing Information Protocol is configured on a Cisco router, by default it is running RIPv1 is display in the output of show ip protocol command, but, the router can only send RIPv1 messages, we can read both RIPv1 and RIPv2 messages. A RIPv1 router ignores the RIPv2 fields in the route entry. We can enable the RIPv2 using the version 2 command in router configuration mode as shown below.

  • Router0(config-router)version 2

Now you can check and verify the version configuration using the show ip protocol command. The Routing Information Protocol process now also includes the subnet mask in all updates, making RIPv2 a classless routing protocol. We can again switch to the version using the below command:

  • Router0(config-router)#no version 2

This command returns the router to the default setting of sending version 1 updates but listening for version 1 or version 2 updates.

Disabling Auto-Summarization

RIPv2 automatically summarizes networks at major network boundaries by default, Just like RIPv1 so, we can modify the default RIPv2 behaviour using the following command:

  • Router0(config-router)#no auto-summary

This command modifies the default RIPv2 behaviour of automatic summarization. In the case of using RIPv1, the command does not affect. After executing this command it should disable route summarization to their classful address at boundary routers. RIPv2 now includes all subnets with their masks in its routing updates. The show ip protocols display and states that automatic network summarization is not in effect. It is important to enabling RIPv2 before automatic summarization is disabled.