320 CHAPTER 31: OSPF C ONFIGURATIONIf the local router works as an area border router (ABR) and a router in the NSSA,this command summarizes Type-5 LSAs transformed from Type-7 LSAs. If therouter is not the router in the NSSA, the summarization is disabled.Setting OSPF RoutePreferenceSince maybe multiple dynamic routing protocols are running on one routerconcurrently, the problem of route sharing and selection between various routingprotocols occurs. The system sets a preference for each routing protocol, whichwill be used in tie-breaking in case different protocols discover the same route.Perform the following configuration in OSPF view.By default, the OSPF preference is 10, and that of the imported external routingprotocol is 150.Configuring OSPF Timers Setting the interval for Hello packet transmissionHello packets are a kind of most frequently used packets, which are periodicallysent to the adjacent router for discovering and maintaining the adjacency, and forelecting DR and BDR. The user can set the Hello timer.According to RFC2328, the consistency of Hello intervals between networkneighbors should be kept. The Hello interval value is in inverse proportion to theroute convergence rate and network load.Perform the following configuration in interface view.By default, p2p and broadcast interfaces send Hello packets every 10 seconds, andp2mp interfaces send Hello packets every 30 seconds.Setting a dead timer for the neighboring routersThe dead timer of neighboring routers refers to the interval in which a router willregard the neighboring router as dead if no Hello packet is received from it. Theuser can set a dead timer for the neighboring routers.Perform the following configuration in interface view.Table 285 Set OSPF route preferenceOperation CommandConfigure a preference for OSPF forcomparing with the other routing protocols preference [ ase ] preferenceRestore the default protocol preference undo preference [ ase ]Table 286 Set the Hello intervalOperation CommandSet the hello interval of the interface ospf timer hello secondsRestore the default hello interval of the interface undo ospf timer helloRestore the default poll interval undo ospf timer poll
