The four routers R1, R2, R3 and R4 enable OSPF to establish neighbor relationships. The topology and related parameters are shown in the figure. R1: ROUTER-ID: 1.1.1.1, G0/0/0 ip address…

Question

Options

• A12.12.12.2
• B12.12.12.3
• C12.12.12.1
• D0.0.0.0
• E2.2.2.2
• F1.1.1.1

• A
  8% (2)
• B
  4% (1)
• D
  71% (17)
• E
  4% (1)
• F
  13% (3)

Explanation

When R2 (the BDR) disconnects, OSPF must hold a new BDR election among the remaining DROthers - R3 and R4. However, both R3 and R4 have a DR priority of 0, which permanently disqualifies a router from being elected DR or BDR. Since no eligible candidate exists, the BDR field in Hello packets reverts to 0.0.0.0, indicating no BDR is present (R1 remains DR, unchanged by the non-preemptive election rules).

Why each distractor is wrong:

• A (12.12.12.2) / E (2.2.2.2): R2's IP and Router-ID are irrelevant - R2 is offline. Its former BDR role does not persist after disconnection.
• C (12.12.12.1) / F (1.1.1.1): R1's IP and Router-ID identify the DR, not the BDR. R1 keeps the DR role.
• B (12.12.12.3): R3 has priority 0 - it is constitutionally ineligible for BDR regardless of circumstances.

Memory tip: Think of priority 0 as a "spectator-only" flag - that router watches elections but can never win one. If all remaining candidates are spectators, the BDR slot goes to 0.0.0.0.

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