1-3Figure 1-1 A sample routing tableRouter ARouter BRouter HRouter E16.0.0.217.0.0.315.0.0.0 12.0.0.017.0.0.011.0.0.016.0.0.013.0.0.014.0.0.0Router CRouter DRouter FRouter G11.0.0.112.0.0.112.0.0.215.0.0.115.0.0.217.0.0.116.0.0.113.0.0.113.0.0.214.0.0.114.0.0.214.0.0.314.0.0.417.0.0.211.0.0.213.0.0.3Destination Network Nexthop Interface11.0.0.0 11.0.0.1 212.0.0.0 12.0.0.1 113.0.0.0 12.0.0.2 114.0.0.0 14.0.0.4 315.0.0.0 14.0.0.2 316.0.0.0 14.0.0.2 317.0.0.0 11.0.0.2 2Routing Protocol OverviewStatic Routing and Dynamic RoutingStatic routing is easy to configure and requires less system resources. It works well in small, stablenetworks with simple topologies. Its major drawback is that you must perform routing configurationagain whenever the network topology changes; it cannot adjust to network changes by itself.Dynamic routing is based on dynamic routing protocols, which can detect network topology changesand recalculate the routes accordingly. Therefore, dynamic routing is suitable for large networks. Itsdisadvantages are that it is difficult to configure, and that it not only imposes higher requirements on thesystem, but also consumes a certain amount of network resources.Routing Protocols and Routing PriorityDifferent routing protocols may find different routes to the same destination. However, not all of thoseroutes are optimal. In fact, at a particular moment, only one protocol can uniquely determine the currentoptimal route to the destination. For the purpose of route selection, each routing protocol (includingstatic routes) is assigned a priority. The route found by the routing protocol with the highest priority ispreferred.The following table lists some routing protocols and the default priorities for routes found by them:
