28 CONFIGURING RIP
This chapter covers the following topics:
■RIP Overview
■Configure RIP
■Displaying and Debugging RIP
■RIP - Unicast Configuration Example
■Troubleshooting RIP
RIP Overview The Routing Information Protocol (RIP) is an interior gateway and dynamic routing
protocol based on the Distance-Vector (D-V) routing algorithm. RIP uses User
Datagram Protocol (UDP) packets to exchange routing information and adopts
hop count to measure the distance from the destination, called the routing cost. In
RIP, a hop count that is equal to or larger than 16 is defined as infinity (the
destination network or host is unreachable) so RIP is generally applied to
medium-sized networks, such as a campus network. RIP is not designed for
complicated and large-sized networks.
RIP has two versions, RIP-1 and RIP-2. RIP-2 supports simple text authentication
and MD5 authentication, as well as the variable-length sub-net masks.
To improve performance and prevent route loops, RIP supports split-horizon,
poisoned reverse using triggered update. This allows the importation of routes
that are obtained by other routing protocols.
Each router that runs RIP manages a database that includes route items of all
reachable routers on the network. A route item includes the following
information.
■Destination address: The address of the host or network.
■Next-hop address: The address of the next router through which this route
passes to get to the destination.
■Interface: The interface where messages are forwarded.
■Metric value: The overhead for the router to get to the destination. It is an
integer ranging from 0 to16.
■Timer: The last time the route item was modified.
■Route tag: The tag indicates whether it is an internal routing protocol route or
an external routing protocol route.