What are two reasons that an OSPF router does not have any type 5 tank-state advertisements (LSAs) In its link-stale database (LSD6)? (Choose two.)

OSPF Type 5 LSAs (Autonomous System External LSAs) are generated exclusively by an Autonomous System Border Router (ASBR) to advertise routes external to the OSPF domain. If the OSPF network lacks an ASBR, no Type 5 LSAs will be generated or exist in the Link-State Database (LSDB). Additionally, OSPF stub areas (including standard stub and totally stubby areas) are explicitly designed to block Type 5 LSAs from entering the area to reduce database size and memory overhead, replacing them with a default route injected by the Area Border Router (ABR).

B: OSPF requires routers within the same area to maintain identical LSDBs; prefix-lists cannot be used to filter outbound Type 5 LSAs to specific peers.

D: Blocking IP protocol 89 (OSPF) would prevent the OSPF adjacency from forming entirely, resulting in the absence of all LSA types, not just Type 5.

1. Fortinet, "NSE 7 Advanced Routing 7.2 Study Guide," Chapter 3: OSPF, sections on LSA Types and Stub Areas.

2. Moy, J. (1998). "OSPF Version 2," RFC 2328, Section 12.4.3 (AS-external-LSAs). https://doi.org/10.17487/RFC2328