RIP Routing Information Protocol is a distance vector routing protocol used for various small networks. Here are a few characteristics of RIP:

• RIP sends out periodic updates every 30 seconds.
• RIP sends out the full routing table after every periodic update.
• RIP uses distance as it’s metric.
• RIP uses the Bellman-Ford Distance Vector routing protocol for choosing the best path.
• RIP utilizes UDP port 520.
• RIP’s administrative distance is 120.

RIP has a maximum hop count of 15. If the network exceeds the maximum limit of 16 hops, it is considered unreachable to RIP. This is called a Poison Route.

Further, If the distance metric is the same for different links, the RIP protocol load balances the traffic based on the Round Robin Method, which sometimes leads to congestion.

There are two versions of RIP protocols: RIPv1 and RIPv2.

Understanding RIPv1

RIPv1 is a classful protocol that does not support subnet masks, while, RIPv2 is a classless protocol that supports subnet masks and VLSMs.

• RIPv1 sends out broadcasts to 255.255.255.255.
• RIPv2 sends out multicasts using 224.0.0.9.
• Encrypted authentication can be configured between RIPv2.
• Tagging is also supported.

Basic Configurations of RIPv1

Routing protocol configuration occurs in global configuration mode.

To configure RIP on Router A:

Router # router rip
Router # network 172.16.0.0
Router # network 172.17.0.0

Configure RIP on Router B:

Router # router rip
Router # network 172.17.0.0
Router # network 172.18.0.0

To show the routing table, use the command:

Router # show ip route

Basic Configuration of RIPv2

RIPv2 overcomes the limitations of RIPv1. By default, Cisco routers work on RIPv1. To convert the mode to RIPv2, set the command version to 2.

Here is the basic configuration for the RIPv2 command:

Router(config)# router rip
Router(config-router)# version 2

To configure Router A as RIPv2:

RouterA(config)# router rip
Router(config-router)# version 2
Router(config-router)# network 10.0.0.0
Router(config-router)# network 192.168.123.0

There are four basic timers in the RIP Routing Information protocol:

• Update Timer: Indicates how often the router sends routing table updates (30 seconds).
• Invalid Timer: Indicates how long this route exists in the routing table (180 seconds).
• Hold-down Timer: Indicates how long RIP suppresses the route in the routing table. RIP will not update the routing table for new routes until the hold-down timer expires.
• Flush Timer: Indicates how long the route remains in the routing table before being flushed. If no new update comes about that timer, it runs the timer.

Learn: Difference Between Static And Dynamic Routing | Explained With Configuration Guide

What is Split Horizon?

Split Horizon is the mechanism in which the routing update is not sent back through the interface where the route came from.

What is Route Poisoning?

Without expiring the timeout, sending the routing update to other routes when one route fails. This update is sent out on all interfaces with an infinity metric.