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Difficulty: MediumOSPFv2 Neighbor Adjacencies and Router ID

Two Cisco routers are attempting to establish an OSPFv2 adjacency over a point-to-point link. During the neighbor formation process, the routers exchange empty Database Description (DBD) packets to negotiate the Master/Slave relationship and select the initial sequence number. In which specific OSPF neighbor state does this negotiation take place?

Answer: ExStart / EXSTART / ExStart state / exstart

Answer

ExStart
In the ExStart state, neighbor routers use empty Database Description (DBD) packets to determine which router acts as the Master and which acts as the Slave, as well as set the initial DBD sequence number. The router with the higher Router ID wins the Master role.

Step-by-Step Solution

1
Identify the OSPF neighbor state where Master/Slave election occurs
The ExStart (Exchange Start) state is designated for establishing the Master/Slave relationship.
Before exchanging Link State Advertisements (LSAs), routers must determine which device controls the sequence numbering of DBD packets.
2
Verify the role of DBD packets in this state
In ExStart, empty DBD packets containing the MS (Master/Slave), Init, and More bits are exchanged along with Router IDs.
The router with the higher Router ID becomes the Master.

Key Concept

OSPF Neighbor States (ExStart)
Estimated Time:1m 0s
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Topics

OSPFv2 Neighbor Adjacencies and Router ID

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