Configuring OSPF Network Types 295area, these LSAs will be translated into type 5 LSAs for advertisement to otherareas.Non-backbone areas exchange routing information via the backbone area.Therefore, the backbone and non-backbone areas, including the backbone itselfmust maintain connectivity.If necessary physical links are not available for this connectivity maintenance, youcan configure virtual links to solve it.Prerequisites Before configuring an OSPF area, you have configured:■ IP addresses for interfaces, making neighboring nodes accessible with eachother at the network layer.■ OSPF basic functions.Configuration Procedure Follow these steps to configure OSPF area parameters:n ■ It is required to use the stub command on routers attached to a stub area.■ It is required to use the nssa command on routers attached to an NSSA area.■ Using the default-cost command only takes effect on the ABR of a stub areaor the ABR/ASBR of an NSSA area.Configuring OSPFNetwork TypesOSPF classifies networks into four types upon link layer protocols. Since an NBMAnetwork must be fully meshed, namely, any two routers in the network must havea virtual link in between. In most cases, however, the requirement cannot besatisfied, so you need to change the network type using commands.To do… Use the command… RemarksEnter system view system-view -Enter OSPF view ospf [ process-id | router-idrouter-id ] *-Enter area view area area-id -Configure the area as astub areastub [ no-summary ] OptionalNot configured by defaultConfigure the area as anNSSA areanssa [ default-route-advertise| no-import-route |no-summary ] *OptionalNot configured by defaultSpecify a cost for thedefault route advertised tothe stub or NSSA areadefault-cost cost OptionalDefaults to 1.Configure a virtual link vlink-peer router-id [ helloseconds | retransmit seconds |trans-delay seconds | deadseconds | simple [ plain |cipher ] password | { md5 |hmac-md5 } key-id [ plain |cipher ] password ] *OptionalConfigured on both ends of avirtual linkNote that hello and deadparameters must be identicalon both ends of the link.Advertise a host route host-advertise ip-address cost OptionalNot advertised by default
