300-440 Question 119
Single answerAn enterprise network has an OSPF backbone area (Area 0) and a non-backbone area (Area 1). Due to network changes, the non-backbone area has become discontiguous and is unable to directly connect to Area 0. As a network engineer, how can you ensure OSPF connectivity between Area 1 and Area 0?
- A
Configure an OSPF virtual link between an Area 1 router and a router in Area 0.
- B
Convert Area 1 into a stub area to re-establish communication with Area 0.
- C
Configure an OSPF virtual link through a transit area that connects Area 1 and Area 0.
- D
Enable redistribution between OSPF and another routing protocol to bypass OSPF areas.
Show answer and explanation
Correct answer: C
Explanation
OSPF requires all non-backbone areas to have direct or logical connectivity to the backbone area (Area 0). In cases where a non-backbone area becomes discontiguous from Area 0, a virtual link can be configured through a common transit area to restore logical OSPF connectivity. This approach ensures proper OSPF operation without reconfiguring the area types or introducing other protocols.
- A. Incorrect.
Incorrect: A virtual link cannot be directly configured between a non-backbone area (Area 1) and the backbone area (Area 0) unless there is a common transit area.
- B. Incorrect.
Incorrect: Converting Area 1 into a stub area will not resolve the lack of direct connectivity between Area 0 and Area 1.
- C. Correct.
Correct: An OSPF virtual link can be configured through a transit area (e.g., another connected area) to establish logical connectivity between the discontiguous Area 1 and the backbone Area 0.
- D. Incorrect.
Incorrect: Redistribution between OSPF and another routing protocol is not required to resolve the discontiguity issue and would add unnecessary complexity in this case.