290 CHAPTER 33: RIP C ONFIGURATION■ Garbage-collection timer: An unreachable route will be completely deletedfrom the routing table if no update packet for the route is received from theneighbor before this timer times out.RIP Startup andOperationThe whole process of RIP startup and operation is as follows:■ Once RIP is enabled on a router, the router broadcasts or multicasts a requestpacket to its neighbors. Upon receiving the packet, each neighbor running RIPanswers a response packet containing its routing table information.■ When this router receives a response packet, it modifies its local routing tableand sends an update triggering packet to the neighbor. Upon receiving theupdate triggering packet, the neighbor sends the packet to all its neighbors.After a series of update triggering processes, each router can get and keep theupdated routing information.■ By default, RIP sends its routing table to its neighbors every 30 seconds. Uponreceiving the packets, the neighbors maintain their own routing tables andselect optimal routes, and then advertise update information to their respectiveneighbors so as to make the updated routes known globally. Furthermore, RIPuses the timeout mechanism to handle the timeout routes so as to ensurereal-time and valid routes.RIP is commonly used by most IP router suppliers. It can be used in most campusnetworks and the regional networks that are simple and less dispersive. For largerand more complicated networks, RIP is not recommended.Introduction to RIPConfiguration Tasks Table 213 RIP configuration tasksConfiguration Task Description Related sectionConfiguring Basic RIPFunctionsEnabling RIP globallyand on the interface ofa specified networksegmentRequired “Enabling RIPglobally and on theinterface of aspecified networksegment” on page292Setting the RIPoperating status on aninterfaceOptional “Setting the RIPoperating status onan interface” onpage 292Specifying the RIPversion on an interfaceOptional “Specifying the RIPversion on aninterface” on page292
