Refer io the exhibit. While applying the configurations on two routers an engineer notices that OSPF adjacency Between them remains down. Through the ping test the engineer confirmed that both me…

Question

Exhibit

Options

• AEnter the command ip ospf authentication in R2 interface
• BEnable OSPF just inside the router OSPF process not in the interfaces of any router
• CDelete the area 0 authentication message-digest command from the OSPF process in R1
• DDelete the area 0 authentication message-digest command from the OSPF process in R2

• A
  75% (21)
• B
  7% (2)
• C
  14% (4)
• D
  4% (1)

Explanation

Option A is correct because the exhibit shows R1 using area-level plain-text authentication (area 0 authentication) while R2 has area-level MD5 authentication (area 0 authentication message-digest) configured on its OSPF process. Adding ip ospf authentication directly on R2's interface overrides the area-level MD5 setting, forcing R2 to use plain-text authentication - matching R1 and allowing the adjacency to reach Full state.

Option B is wrong because OSPF is already running on both routers (Layer 3 reachability is confirmed), and removing interface-level OSPF configuration would break adjacency further rather than fix it - this doesn't address the authentication mismatch.

Option C is wrong because R1 is configured with area 0 authentication (plain-text), not area 0 authentication message-digest, so that command does not exist on R1 and cannot be deleted.

Option D is wrong because deleting area 0 authentication message-digest from R2 would leave R2 with no authentication, which still mismatches R1's plain-text authentication requirement - adjacency would remain down.

Memory tip: Think "interface beats area" - interface-level OSPF authentication always overrides area-level authentication. Whenever you see OSPF adjacency failing despite confirmed Layer 3 reachability, immediately suspect an authentication type mismatch between routers.

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