3Com Router 3000 Ethernet FamilyConfiguration Guide Chapter 3 RIP Configuration3Com Corporation3-1Chapter 3 RIP ConfigurationNote:For the parameter explanation of VPN instance, refer to "MPLS" module of this manual.3.1 RIP OverviewRIP (Routing Information Protocol) is a relatively simple interior gateway protocol (IGP),and it is primarily applied to relatively small networks.Since the implementation of RIP is comparatively simple, the impact of the cost of theprotocol itself on the performance of networks is relatively small, and the configurationand maintenance of RIP is easier than that of OSPF and IS-IS, RIP is still widely used inpractice.3.1.1 Mechanism of RIPI. Introduction to RIPRIP is a kind of Distance-Vector (D-V) algorithm-based protocol and exchanges routinginformation via UDP packets. It employs Hop Count to measure the distance to thedestination host, which is called Routing Cost. In RIP, the hop count from a router to itsdirectly connected network is 0, and that to a network which can be reached throughanother router is 1, and so on. To restrict the time to converge, RIP prescribes that thecost is an integer ranging from 0 and 15. The hop count equal to or exceeding 16 isdefined as infinite, that is to say, the destination network or the host is unreachable.To improve performance and avoid the creation of routing loops, RIP supports both SplitHorizon and Poison Reverse. Besides, RIP can also redistribute routes from otherrouting protocols.II. Route database of RIPEach router running RIP manages a route database, which contains routing entries toall the reachable destinations in the network. These routing entries contain thefollowing information:z Destination address: IP address of a host or a network.z Next hop address: The address of the next router that a router will pass through forreaching the destination.z Interface: The interface through which the IP packet should be forwarded.
