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Difficulty: MediumOSPFv2 Neighbor Adjacencies and Router ID

A network engineer is configuring OSPFv2 on a broadcast multiaccess Ethernet network segment connecting two Cisco routers. Which two parameters must match between the connected router interfaces for an OSPFv2 neighbor adjacency to form successfully? (Select two.)

  1. OSPF Area IDAnswer
  2. OSPF Hello and Dead timer intervalsAnswer
  3. C
    OSPF Process ID
  4. D
    OSPF Router ID

Answer

The parameters that must match between neighboring routers for an OSPFv2 adjacency to form are the OSPF Area ID and the OSPF Hello and Dead timer intervals.
For two routers to establish an OSPFv2 neighbor adjacency on a broadcast segment, several parameters in the OSPF Hello packets must match, including the Area ID, IPv4 subnet mask, Hello/Dead timer intervals, and authentication type/key.

Step-by-Step Solution

1
Identify mandatory matching parameters contained in OSPF Hello packets
OSPF neighbor adjacencies require matching Area ID, Subnet Mask, Hello and Dead Timers, and Authentication fields.
A mismatch in any of these Hello packet fields prevents routers from progressing past the Init neighbor state.
2
Evaluate non-matching and unique OSPF configuration parameters
OSPF Process ID is locally significant, while OSPF Router ID must be globally unique across the autonomous system.
Process IDs are not communicated across neighbor links, and duplicate Router IDs cause database synchronization failures.

Key Concept

OSPFv2 Neighbor Adjacency Requirements
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Topics

OSPFv2 Neighbor Adjacencies and Router ID

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