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H12-821_V1.0 · Question #834

In network A, the two DRother devices will not establish an adjacency relationship, and their status will remain in 2-way.

The correct answer is A. TRUE. Option A is correct because in OSPF, DRother routers only form full adjacencies with the DR (Designated Router) and BDR (Backup Designated Router) - never with each other. Two DRother routers exchange Hello packets and recognize each other as neighbors, which brings them to…

IPv4 Routing Technologies

Question

In network A, the two DRother devices will not establish an adjacency relationship, and their status will remain in 2-way.

Options

  • ATRUE
  • BFALSE

How the community answered

(38 responses)
  • A
    71% (27)
  • B
    29% (11)

Explanation

Option A is correct because in OSPF, DRother routers only form full adjacencies with the DR (Designated Router) and BDR (Backup Designated Router) - never with each other. Two DRother routers exchange Hello packets and recognize each other as neighbors, which brings them to 2-Way state, but they stop there and do not proceed through the remaining OSPF adjacency stages (ExStart, Exchange, Loading, Full).

Option B is wrong because it contradicts a core OSPF design principle: the DR/BDR election exists precisely to reduce the number of adjacencies on a multi-access network (like Ethernet). Without this rule, every router would need a full adjacency with every other router, creating O(n²) adjacencies.

Memory tip: Think of the DR/BDR as a "hub" - DRother routers are like spokes that only connect to the hub (DR/BDR), never to each other. The 2-Way state between DRothers is OSPF saying "I see you, but I'm not talking to you directly."

Topics

#OSPF adjacency#DR/BDR/DRother#2-way state#multi-access networks

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