59 RIP C ONFIGURATIONWhen configuring RIP, go to these sections for information you are interested in:■ “RIP Overview” on page 971■ “Configuring RIP Basic Functions” on page 976■ “Configuring RIP Advanced Functions” on page 978■ “Optimizing the RIP Network” on page 981■ “Displaying and Maintaining RIP Configuration” on page 986■ “RIP Configuration Example” on page 986■ “Troubleshooting RIP Configuration” on page 990RIP Overview RIP is a simple Interior Gateway Protocol (IGP), mainly used in small-sizednetworks, such as academic networks and simple structured LANs. RIP is notapplicable to complex networks.RIP is still widely used in practical networking due to easier implementation,configuration and maintenance than OSPF and IS-IS.RIP Working Mechanism Basic concept of RIPRIP is a Distance-Vector (D-V)-based routing protocol, using UDP packets forexchanging information through port 520.RIP uses a hop count to measure the distance to a destination. The hop count isknown as metric. The hop count from a router to its directly connected network is0. The hop count of a network reachable through one router is 1. To limitconvergence time, the range of RIP metric value is from 0 to 15. A metric value of16 (or bigger) is considered infinite, which means the destination network isunreachable. That is why RIP is not suitable for large-scaled networks.RIP prevents routing loops by implementing the split horizon and poison reversefunctions.RIP routing tableEach RIP router has a routing table containing routing entries of all reachabledestinations, and each routing entry contains:■ Destination address: IP address of a host or a network.■ Next hop: IP address of the adjacent router’s interface to reach the destination.■ Egress interface: Interface through which the router forwards the packets tothe destination.■ Metric: Cost from the local router to the destination.
