Virtual Link for Connecting New Equipment in a Stub OSPF Area

A

In OSPF (Open Shortest Path First) routing protocol, there are different types of areas such as backbone area (Area 0), standard area, totally stubby area, not-so-stubby area (NSSA), and stub area. Each area has its own set of characteristics and behaviors.

In a stub area, there is no transit traffic, which means that the area has only one exit point, which is the ABR (Area Border Router) to the backbone area. The purpose of creating a stub area is to reduce the size of the OSPF routing table and to limit the amount of routing information that is exchanged between the routers. In a stub area, the Type 5 External LSAs (Link State Advertisements) are not allowed, which means that the external routes are not advertised into the stub area.

Now, coming back to the question, the supervisor has asked to build a virtual link across the stub area to connect new equipment acquired in a recent ISP acquisition. A virtual link is used to connect two non-backbone areas through a backbone area. Virtual links are used when there is no physical connection between two areas, and it is not possible to create a direct connection.

Option A: Type 5 LSAs would be blocked in a stub area. This statement is true for a stub area. Type 5 LSAs are External LSAs, and they are not allowed in a stub area. If a Type 5 LSA is received in a stub area, it is discarded.

Option B: Type 5 LSAs would carry external information across your transit area to the backbone. This statement is not true for a stub area. In a stub area, Type 5 LSAs are not allowed, and they are not forwarded to the backbone area.

Option C: Type 5 LSAs would be seen only in the newly attached area. This statement is not true for a stub area. Type 5 LSAs are External LSAs, and they are not allowed in a stub area. If a router in the newly attached area generates a Type 5 LSA, it will not be flooded to the rest of the routers in the stub area.

Option D: Type 5 LSAs would be converted to Type 7 LSAs. This statement is true for an NSSA (Not-So-Stubby Area) and not for a stub area. In an NSSA, Type 5 LSAs are converted to Type 7 LSAs at the ASBR (Autonomous System Boundary Router), and then they are flooded to the rest of the NSSA. However, in a stub area, Type 5 LSAs are not allowed, and there is no conversion to Type 7 LSAs.

Therefore, the correct answer is A. Type 5 LSAs would be blocked in a stub area.