300-440 Question 116
Select 2A network engineer is troubleshooting OSPF connectivity between two areas in their network. The network consists of Area 0 and Area 2, but there is no direct connection between them. To resolve the issue, the engineer decides to implement a virtual link. Which of the following requirements must be met for the virtual link to function properly?
- A
The virtual link must traverse a common area between Area 0 and Area 2.
- B
The area used for the virtual link must not be a stub area.
- C
The virtual link is configured between the ABR in Area 0 and the ABR in Area 2.
- D
The virtual link requires authentication to be configured.
- E
The virtual link is used to connect two totally stubby areas.
Show answer and explanation
Correct answers: A, B
Explanation
A virtual link in OSPF is used to connect a non-contiguous area to the backbone area (Area 0) via a transit area. For the virtual link to function, it must be configured over a common (transit) area between the two ABRs, and the transit area cannot be a stub area. Authentication is optional, and virtual links are not used to connect stub or totally stubby areas directly.
- A. Correct.
Correct: For a virtual link to function, it must traverse a common area (known as a transit area) between the disconnected areas, such as Area 0 and Area 2.
- B. Correct.
Correct: The transit area used for the virtual link cannot be a stub area because stub areas block LSAs necessary for OSPF operation over the virtual link.
- C. Incorrect.
Incorrect: Virtual links are not directly configured between ABRs in disconnected areas but rather between the ABRs in the transit area and Area 0.
- D. Incorrect.
Incorrect: While OSPF virtual links can optionally support authentication, it is not a mandatory requirement for the virtual link to function.
- E. Incorrect.
Incorrect: Virtual links are not used to connect two totally stubby areas; they are specifically designed to connect non-contiguous OSPF areas to Area 0.