432 C HAPTER 15: IPX ROUTINGRIP operates with active and passive network devices:n Active devices — Usually routers, they broadcast their RIP messagesto all devices in a network; they update their own routing tables whenthey receive a RIP message.n Passive devices — Usually hosts, they listen for RIP messages andupdate their routing tables; they do not send RIP messages.On your system, you select a RIP mode to determine how RIP operates, asdescribed in “IPX RIP Mode” later in this chapter.An active router sends a RIP message every 60 seconds. This messagecontains both the network number for each destination network and thenumber of hops to reach it. In RIP, each router through which a packetmust travel through to reach a destination counts as one network hop.Routing Tables A routing table collects information about all intranetwork segments. Thistable allows a router to send packets toward their destinations over thebest possible routes.The table contains an entry for every network number that the routerknows about. The router uses this information when the router is notdirectly connected to a packet’s destination network. The routinginformation table provides the address of another router that can forwardthe packet toward its destination.The routing table consists of the following elements:n Interface — The interface number of the router that is used to reacha network segmentn Address — The network segments that the router knows aboutn Hops to network — The number of routers that must be crossed toreach a network segmentn Tiks to network — An estimate of the time in seconds that isnecessary to reach a network segmentn Node — The node address of the router that can forward packets toeach network segment. When the node is set to all 0s, the router isdirectly connected.n Aging timer — The time in seconds since the network’s last update
