On an office network of an enterprise, OSPF is enabled on two directly connected routers. During adjacency establishment, the state machine stays in the 2-way state. Which of the following statements are not possible causes?
A.
Hello time values are different.
B.
Area IDs are different.
C.
Router IDs conflict.
D.
The N-bit and E-bit of Hello packets are the same.
Comprehensive and Detailed Step-by-Step Explanation:
OSPF State Machine:
OSPF adjacency progresses through several states: Down > Init > 2-Way > ExStart > Exchange > Loading > Full.
The 2-Way state indicates that routers have exchanged Hello packets but are not forming full adjacencies.
Possible Causes for Staying in the 2-Way State:
Hello Time Values Are Different (A): Mismatched Hello/Dead intervals prevent adjacency establishment.
Area IDs Are Different (B): OSPF routers must belong to the same area to establish adjacency.
Router IDs Conflict (C): While Router ID conflicts cause other issues, they do not result in the 2-Way state.
N-bit and E-bit Are the Same (D): Matching N-bit/E-bit values are normal and do not cause problems.
[References:, HCIA-Datacom Study Guide, Chapter: OSPF Adjacency Establishment, Huawei OSPF Neighbor State Analysis, , , ]
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