![]() To ensure reachability of AS external routes and inter-area routes, the ABR in a totally stub area advertises Type 3 default routes to the entire totally stub area. In a totally stub area, a router maintains fewer routing entries in the routing table and transmits less routing information. All AS external routes must be advertised by ABRs.Ī totally stub area does not advertise AS external routes or inter-area routes, but only intra-area routes. To ensure reachability of AS external routes, the ABR in a stub area advertises Type 3 default routes to the entire stub area. In a stub area, a router maintains fewer routing entries in the routing table and transmits less routing information. It is usually named area 0.Ī stub area does not advertise AS external routes, but only intra-area and inter-area routes. A backbone area connects to all the other OSPF areas.A standard area is the most common area and transmits intra-area routes, inter-area routes, and external routes.Common areas include standard areas and backbone areas. At present, there are no applications of Type 11 LSAs. Type 11 LSAs are advertised within an AS.LSAs used to support TE are a type of Type 10 LSAs. Type 10 LSAs are advertised inside an OSPF area.Grace LSAs used to support GR are a type of Type 9 LSAs. Type 9 LSAs are advertised only on the network segment where the interface originating Type 9 LSAs resides.Provides a universal mechanism for OSPF extension. ![]() NSSA-LSAs are generated by an ASBR and advertised in NSSAs only. AS-external-LSAs are generated by an ASBR and advertised to all areas except stub areas and NSSAs.ĭescribes routes to a destination outside the AS. ![]() ASBR-summary-LSAs are generated by an ABR and advertised to all related areas except the area to which the ASBR belongs.ĭescribes routes to a destination outside the AS. The Type 3 LSA of the network segment 11.1.1.0 generated by the ABR for area 0 and the Type 3 LSA of the network segment 10.1.1.0 generated by the ABR for area 1 are advertised within the non-totally stub area or NSSA.ĭescribes routes to an Autonomous System Boundary Router (ASBR). Area 0 has a network segment 10.1.1.0, and area 1 has a network segment 11.1.1.0. For example, an ABR belongs to both area 0 and area 1. Network-summary-LSAs are generated by an Area Border Router (ABR) and advertised in all areas except totally stub areas and Not-So-Stubby Areas (NSSAs). Network-LSAs are generated by a designated router (DR) and advertised in the area to which the DR belongs.ĭescribes routes to a specific network segment in an area. It is generated by every router and advertised in the area to which the router belongs.ĭescribes the link status of all routers on the local network segment. ![]() The router can obtain a new router ID only after a router ID is reconfigured for the router or an OSPF router ID is reconfigured and the OSPF process restarts.ĭescribes the link status and link cost of a router. If no loopback interface is configured, the router selects the largest IP address among other interface addresses as its router ID.Īfter the router has been running OSPF and selected its router ID, it still uses this router ID if the interface whose IP address is used as the router ID is Down or disappears (for example, the undo interface loopback loopback-number command is run) or a larger interface IP address exists.The router preferentially selects the largest IP address among loopback interface addresses as its router ID.A router selects its router ID based on the following rules: If no router ID is manually configured for a router, the router selects an interface IP address as its router ID.It is recommended that you manually configure a router ID to ensure OSPF stability.A router ID is a 32-bit unsigned integer, uniquely identifying a router in an AS.Ī router ID can be manually configured or automatically selected by a router: A router requires a router ID if it is to run OSPF.
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