A Type 1 LSA, or Router LSA, is an OSPF advertisement generated by every router to describe that router’s links. Routers carry LSAs in LSU messages and store them in the link-state database (LSDB). section 18.4
Use these distinctions when reading an OSPF LSDB:
- Every router advertises one Type 1 LSA; the LSDB should contain a Router LSA for each router. section 18.4
- A Type 2 LSA is different: the designated router generates it for a broadcast segment and lists the routers on that segment. section 18.5
- A Type 5 LSA advertises external routes and is generated by an ASBR, such as for a default route. section 18.4
Inspecting the LSDB
Run `show ip ospf database`. The Router Link States section lists Type 1 LSAs, one for each OSPF router. In the example topology, five routers advertise Type 1 LSAs; R5 adds a Type 2 LSA and R1 adds a Type 5 LSA. section 18.4
Figure 18.14 An OSPF AS and the contents of its LSDB. Each router advertises a type 1 (Router) LSA. R5, as the DR of the R2–R3–R4–R5 segment, advertises a type 2 (Network) LSA. R1, as an ASBR, advertises a type 5 LSA.
Use the topology and LSDB figure to compare each router’s Type 1 advertisement with the Type 2 and Type 5 LSAs. section 18.4
