In the network shown in the figure, OSPF runs on four routers, and they are in the same area and the same network segment. OSPF will automatically elect a DR and a BDR, and the other two routers…

Question

Options

• ATRUE
• BFALSE

• A
  18% (6)
• B
  82% (27)

Explanation

Option B is correct because the stated purpose of DR/BDR election is wrong. While OSPF does elect a DR and BDR on multi-access (broadcast) network segments, the primary reason is to reduce the number of OSPF adjacencies and control LSA flooding overhead - not to achieve a "backup effect." Without DR/BDR, every router would need a full adjacency with every other router (n(n-1)/2 adjacencies), which is inefficient at scale.

Option A (TRUE) is incorrect on two counts: the mechanics described (4 routers → 1 DR, 1 BDR, 2 DROthers) are accurate, but attributing the purpose to "backup" misrepresents the design goal. The BDR does provide failover if the DR goes down, but that is a secondary benefit, not the driving rationale.

Memory tip: Think "DR = Designated Router = Efficiency, not just Emergency." The DR/BDR mechanism is an optimization tool first (fewer adjacencies, fewer LSAs), with failover capability as a bonus - exam questions that describe it purely as a "backup" mechanism are flagging a false premise.

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