OSPF 2WAY State: NBMA Neighbor Configuration

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  R6 has formed a full adjacency with neighbor 1.1.1.1.

  Why it's wrong here

  The OSPF neighbor state shown is 2WAY, not FULL. In the state machine, 2WAY is reached after two routers exchange Hello packets that list each other's Router ID, proving bidirectional reachability. A FULL adjacency requires the Database Description, LSR, LSU, and LSAck packet exchange to synchronize link-state databases. On broadcast multi-access networks, FULL neighbors are normally only formed with the DR/BDR; a non-DR/BDR router that reaches 2WAY with another non-DR/BDR router stays at 2WAY indefinitely.

• ✗

  The hello packet was sent to the DR/BDR multicast address 224.0.0.6.

  Why it's wrong here

  The destination IP in the captured Hello is 224.0.0.5, which is the AllSPFRouters multicast address. OSPF routers send Hello packets to 224.0.0.5 on broadcast networks so that every OSPF-speaking router on the segment receives them. The 224.0.0.6 AllDRouters address is used only when a router sends OSPF packets specifically to the DR/BDR, such as Link-State Updates sent by a non-DR router to the DR/BDR. Since this is a Hello, it would never be sent to 224.0.0.6, so this option is incorrect.

• ✓

  R6 and 1.1.1.1 are neighbors, but a full adjacency may not yet be formed.

  Why this is correct

  The 2WAY state confirms that R6 and 1.1.1.1 have exchanged Hello packets that include each other's Router ID, making them OSPF neighbors. However, 2WAY is only a preliminary step; a full adjacency (FULL) requires an exchange of Database Description packets, Link-State Requests, and Link-State Updates to synchronize their OSPF link-state databases. Moreover, on broadcast multi-access networks, a router forms FULL adjacencies only with the DR/BDR, so two non-DR routers can remain in 2WAY without ever reaching FULL. Thus, being neighbors does not guarantee a full adjacency exists.

• ✗

  The OSPF network type is point-to-point.

  Why it's wrong here

  On a point-to-point OSPF network type, there is no DR/BDR election and routers transition directly from Down to Init to 2WAY and then immediately to ExStart/Exchange/FULL without an extended 2WAY wait. The fact that R6 is stuck in the 2WAY state indicates the network is not point-to-point. For point-to-point links, OSPF also uses a different Hello timer behavior and does not rely on multicast DR/BDR addressing, which is inconsistent with the capture showing a broadcast-style Hello on 224.0.0.5. Therefore, the OSPF network type cannot be point-to-point under these conditions.