300-410 Question 104
Single answerA network engineer is configuring OSPF on a network that includes both point-to-point and nonbroadcast multi-access (NBMA) links. The engineer needs to ensure that OSPF adjacency is established correctly on all links. Which OSPF network type configuration is required on the NBMA link to allow the routers to form adjacencies without manual neighbor configuration?
- A
Broadcast
- B
Point-to-point
- C
Nonbroadcast
- D
Point-to-multipoint
Show answer and explanation
Correct answer: A
Explanation
In OSPF, NBMA links do not inherently support multicast or broadcast communication, which complicates neighbor discovery. Configuring the OSPF network type as 'Point-to-multipoint' on an NBMA network allows the routers to automatically discover and form adjacencies with neighbors without requiring manual configuration. This simplifies network management and ensures OSPF operates correctly. The other options either require manual neighbor configuration or are not designed for NBMA environments.
- A. Correct.
Broadcast is used in environments like Ethernet where multicast and broadcast traffic is inherently supported. However, NBMA environments do not support broadcast or multicast by default, so this would not work without additional configuration.
- B. Incorrect.
Point-to-point is not suitable for NBMA links because NBMA typically connects multiple routers. Point-to-point is designed for direct, one-to-one connections.
- C. Incorrect.
Nonbroadcast is commonly used on NBMA links, but it requires manual neighbor configuration because routers do not automatically discover neighbors. This does not meet the requirement in the question.
- D. Incorrect.
Point-to-multipoint is a suitable OSPF network type for NBMA environments, as it allows routers to form adjacencies without manual neighbor configuration. It treats the network as a series of point-to-point links, enabling automatic neighbor discovery.