1.2 RIP Version 2  
  1.2.1 RIP history  
The Internet is a collection of autonomous systems (AS). Each AS is generally administered by a single entity. Each AS will have its own routing technology, which may differ from other autonomous systems. The routing protocol used within an AS is referred to as an Interior Gateway Protocol (IGP). A separate protocol, called an Exterior Gateway Protocol (EGP), is used to transfer routing information between autonomous systems. RIP was designed to work as an IGP in a moderate-sized AS. It is not intended for use in more complex environments.

RIP v1 is considered an interior gateway protocol that is classful. RIP v1 is a distance vector protocol that broadcasts its entire routing table to each neighbor router at predetermined intervals. The default interval is 30 seconds. RIP uses hop count as a metric, with 15 as the maximum number of hops.

If the router receives information about a network, and the receiving interface belongs to the same network but is on a different subnet, the router applies the one subnet mask that is configured on the receiving interface:

  • For Class A addresses, the default classful mask is 255.0.0.0.
  • For Class B addresses, the default classful mask is 255.255.0.0.
  • For Class C addresses, the default classful mask is 255.255.255.0.

RIP v1 is a popular routing protocol because virtually all IP routers support it. The popularity of RIP v1 is based on the simplicity and the universal compatibility it demonstrates. RIP v1 is capable of load balancing over as many as six equal-cost paths, with four paths as the default.

RIP v1 has the following limitations:

  • It does not send subnet mask information in its updates.
  • It sends updates as broadcasts on 255.255.255.255.
  • It does not support authentication.
  • It is not able to support VLSM or classless interdomain routing (CIDR).

RIP v1 is simple to configure, as shown in Figure .