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Difficulty: EasyOSPFv2 Network Types and DR/BDR Selection

A network engineer configures an OSPFv2 process on a router interface connected to a broadcast multiaccess Ethernet network. The engineer issues the command `ip ospf priority 0` on the interface. How does this specific priority configuration affect the router's role in the OSPF DR/BDR election process?

  1. The interface is strictly prohibited from participating in the election and remains in the DROTHER state.Answer
  2. B
    The interface will still be elected as DR if it has a higher Router ID than all other routers on the multiaccess segment.
  3. C
    The interface automatically defaults to the BDR role while letting the router with priority 1 become the DR.
  4. D
    The interface becomes the DR only if no other neighboring router has an active loopback interface configured.

Answer

Setting an OSPF interface priority to 0 disqualifies the router from participating in elections, forcing its state to DROTHER.
In OSPFv2, interface priority ranges from 0 to 255. A priority of 0 specifically signifies that the router is disqualified from becoming either the Designated Router (DR) or the Backup Designated Router (BDR) on a multiaccess network segment. As a result, the interface transitions to and stays in the DROTHER state.

Step-by-Step Solution

1
Evaluate the effect of the interface subcommand `ip ospf priority <0-255>` on multiaccess networks.
The default priority on multiaccess interfaces is 1.
Higher priority values are preferred during DR/BDR elections.
2
Determine the special significance of priority value 0.
A priority of 0 explicitly makes the interface ineligible to become DR or BDR.
This is a design mechanism used to prevent hub or low-capacity routers from accepting DR/BDR responsibilities.

Key Concept

OSPF Interface Priority 0 Selection Ineligibility
Estimated Time:45s
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Topics

OSPFv2 Network Types and DR/BDR Selection

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