[OSPF] Router Type and LSA Type

Internal router: all its interfaces in Area 0

Backbone router: at least one interface in Area 0

Area Border router: a router with at least one interface in Area 0 and another in a non-backbone area.  All ABRs are backbone routers, but not all backone routers are ABRs.

ASBR(autonomous system boundary router): a router injecting routes into OSPF domain via route redistributuin

 

LSA type

Type1: generate by each router for every area

Type 2: sent out only by DR

Type 1 and 2 confined to a single area, which helps multi-area OSPF reduce the load o router resources. If you had only one large OSPF area, every router in the area would receive every single Type 1 and type 2 LSA

Type 3: summary link advertisements are generated by ABRs and describe inter-area routers. They summarize the networks from on area to anotherr, and are not flooded into a toatal stub area.

Type4 : generate only by ABR and describe the path to the ASBR. Type 4 LSA are not flooded into a toatl stub area

Type 5:

describe links external to the OSPF domain. This link describes the network injected into the OSPF domain via toute redistributeion on R1, verified by the address listed as the advertising router. Type 5 LSA  are generated only by ASBRs and they're flooded to all area except stub and total stub areas.

 

Type 6: a specialty LSA type generated only by routers using multicast extensions to OSPF(MOSPF), while Type 7s are generated only by an ASBR and sent in to a not-so-stub area.

NSSAs act as stub area, but some of the more-specific routes are advertised, rathe than just a default route.

Type 7: flooded throughtout the NSSA, but they don't get to leave! Instead, they're converted to Type 5 LSAs and are then sent out of the NSSA