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ccnac offre d'emploi.The workings of route suppression and suppression timers are not well understood. Here is an example to see how these two mechanisms work together to solve a large routing loop problem, as shown in Figure 14.9, where it is assumed that the router is running RIPvLIn this example, router A has a fault on interface E0, causing its connection to 192.168.1.0 to be broken. Because RIPvl does not use triggered updates, Router A must wait for the periodic timer to expire before it can broadcast its routing information to Router B and Router C. In RIPvl, the periodic update timer is set to 30 seconds. Router A will suppress route 192.168.1.0 (by setting its metric16), and sends it to the other two routers after the periodic update timer expires.After receiving a routing update from Router A that contains a suppressed route, Routers B and C will send reverse suppression to Router A. All routers will freeze the suppressed route in their routing tables until the suppression timer expires. In RIPvl, the suppression timer defaults to 180 seconds. After the periodic timer expires, Router B and Router C also advertise outbound through all of their active interfaces that contain theThe routing update for the suppressed route. During the propagation of this suppressed route, the router that has received it will count down its suppression timer. Router BIf another router in the network advertises a worse path to 192.168.1.0 (with more hops than the route initially advertised by Router A), none of the three routers listed in the network schematic will use it because the suppressed route is frozen in the routing table. The reason for using the suppression timer is that the other routers might advertise the path to 192.168.1.0, but it might not be valid. In other words, the other router may think that it can go to network 192.168.1.0 via router A, and thus indicate that it is reachable. This is because this router has not yet received a suppressed route, but the suppression timers on the other routers ensure that they do not add incorrect routing information to the routing table thatwhich in turn leads to routing loops.During suppression, if Router A's connection to 192.168.1.0 returns to normal, it will indicate to Router B and Router C that this network is reachable. Because Router A advertises the same metric value as previously advertised, Router B and Router C will revoke the suppression timer and replace the suppressed route with the new information.Figure 14.9 Route Suppression and Suppression Timer Example Routing Introduction Understand the basic functions of a router and the protocols being routed and routing protocols. It is important to be familiar with the terminology in this chapter: knowing whatChapter 14 Routers and Routing 349