A Totally Stubby Area in OSPF is a special type of stub area where only intra-area (Type 1) LSAs, router LSAs, and default routes (Type 3 LSA with 0.0.0.0/0) are allowed to be injected. It blocks inter-area routes (Type 3 LSAs for specific prefixes) and Type 5 LSAs (external routes) to reduce the size of the Link-State Database (LSDB) and enhance router performance.
Explanation of the Options:
* A. Type 3 specific LSA - # Correct Answer. These LSAs represent inter-area routes. Totally Stubby Areas do not allow Type 3 LSAs for specific routes, only for the default route (0.0.0.0/0).
* B. Type 1 LSA - # Allowed. These are Router LSAs generated by routers within the area and are necessary for OSPF to function.
* C. Type 3 LSA that describes a default route - # Allowed. This is the only Type 3 LSA permitted in a Totally Stubby Area. It provides a default route (0.0.0.0/0) to reach external destinations.
* D. Type 2 LSA - # Allowed if there are broadcast or NBMA networks in the area. These describe the network segment in multi-access environments and are generated by the DR.
Official Huawei Reference:
# Huawei HCIP-Datacom-Core Technology Study Guide -
Chapter: OSPF Special Areas
* "A totally stub area does not allow inter-area Type 3 LSAs or external Type 5 LSAs to enter. Only a default route is injected in the form of a Type 3 LSA (0.0.0.0/0), which greatly reduces the LSDB size."
# Also refer to:
* Huawei VRP Command Guide > OSPF > Configuration Notes > OSPF Special Areas