The Routing Information Protocol (RIP) was a first generation routing protocol for IPv4 originally specified in RFC 1058. It is easy to configure, making it a good choice for small networks.
RIPv1 has the following key characteristics:
- Routing updates are broadcasted (255.255.255.255) every 30 seconds.
- The hop count is used as the metric for path selection.
- A hop count greater than 15 hops is deemed infinite (too far). That 15th hop router would not propagate the routing update to the next router.
In 1993, RIPv1 evolved to a classless routing protocol known as RIP version 2 (RIPv2). RIPv2 introduced the following improvements:
- Classless routing protocol - It supports VLSM and CIDR, because it includes the subnet mask in the routing updates.
- Increased efficiency - It forwards updates to multicast address 224.0.0.9, instead of the broadcast address 255.255.255.255.
- Reduced routing entries - It supports manual route summarization on any interface.
- Secure - It supports an authentication mechanism to secure routing table updates between neighbors.
The table in the figure summarizes the differences between RIPv1 and RIPv2.
RIP updates are encapsulated into a UDP segment, with both source and destination port numbers set to UDP port 520.
In 1997, the IPv6 enabled version of RIP was released. RIPng is based on RIPv2. It still has a 15 hop limitation and the administrative distance is 120.