Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 4 OSPF Configuration4-19Note:z The import-route command cannot import the default route. To import the defaultroute, you must use the default-route-advertise command.z The filtering of advertised routes by OSPF means that OSPF only converts theexternal routes meeting the filter criteria into Type-5 or Type-7 LSAs andadvertises them.z When enabling OSPF to redistribute routes, you can also configure the defaults ofsome additional parameters, such as cost, number of routes, tag, and type. A routetag can be used to identify protocol-related information.z Use the keyword allow-ibgp with care when redistributing routes from BGP,because it redistributes IBGP routes without keeping the AS_PATH attribute,which may lead to routing loops between ASs.4.7 OSPF Network Adjustment and OptimizationYou can adjust and optimize an OSPF network in the following aspects:z By changing the OSPF packet timers, you can adjust the convergence speed ofthe OSPF network and the network load brought by OSPF packets. On somelow-speed links, you need to consider the delay experienced when the interfacestransmit LSAs.z By adjusting SPF calculation interval, you can mitigate resource consumptioncaused by frequent network changes.z In a network with high security requirements, you can enable OSPFauthentication to enhance OSPF network security.z In addition, OSPF supports network management. You can configure the bindingof the OSPF MIB with an OSPF process and configure the Trap messagetransmission and logging functions.4.7.1 Configuration PrerequisitesBefore adjusting and optimizing an OSPF network, perform the following tasks:z Configuring the network layer addresses of interfaces so that the adjacent nodesare reachable to each other at the network layerz Configuring basic OSPF functions4.7.2 Configuring OSPF TimersThe Hello intervals for OSPF neighbors must be consistent. The value of Hellointerval is in inverse proportion to route convergence speed and network load.
