The LSA type defines different router types. Therefore, multiple LSAs are required. Usually, the test types are Type1, Type2, Type3, Type4, Type5, and Type7.
Type1 is a Router LSA.
All OSPF speaker types generate LSAs of this type. They are only advertised in the area, including the router's own topology information and routing information.
Type2 is a Network LSA.
Type 2 LSAs that occur only on the MA network are generated by the DR and include all network information that is connected to the DR. They are only advertised in the area.
Type3 is a Network summary LSA.
It is generated by the ABR and advertises routing entries outside the router in the area. When there are multiple ABRs, the cost is used to determine the route summary. This cost is a simple sum of external route cost and internal cost generated by the router in the area. metric-Type 1), instead of running the SPF algorithm, it can be said that OSPF is a link state protocol in the area, and a distance vector protocol is between areas. Inter-regional route transfer
Type4 is the ASBR summary.
It is generated by the ABR to broadcast the location of the ASBR. The show IP OSPF database shows that the Type4 LSA is always a host mask 255.255.255.255, and Type4 is the only LSA with no Area attribute in the database.
Type5 is an external summary.
It is generated by an ASBR and is the routing information of non-OSPF devices. Generally, in a large network, there are a large number of such LSAs in the router's database, which imposes a heavier load on the router. Therefore, we can use stub areas to limit the spread of such LSAs. However, consider the following scenario. If a router running OSPF needs to connect to a non-OSPF network, net1, and advertises the route entries in the non-OSPF network to OSPF, and does not want to store a large number of external networks advertised by other routers in the database. Routing, then we can not use STUB, because this will block all the External routes, OSPF network will lose the routing information of net1,
Type7 is therefore written to the OSPF standard.
In order to solve this problem, CISCO stipulates NSSA. Type7 advertises the External Route in NSSA. On the ABR of NSSA, Type7 is converted into Type5 (of course, Type7 LSA P-bit=1), and then these routing entries are notified by the ABR. Backbone.
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