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Difficulty: EasyOSPFv2 Network Types and DR/BDR Selection

A network administrator checks the OSPF status of a router interface connected to an Ethernet broadcast domain and observes the following output:

text
GigabitEthernet0/0 is up, line protocol is up
Internet Address 192.168.10.5/24, Area 0
Process ID 1, Router ID 10.1.1.5, Network Type BROADCAST, Cost: 1
State DROTHER, Priority 0
Designated Router (ID) 10.1.1.1, Interface address 192.168.10.1
Backup Designated router (ID) 10.1.1.2, Interface address 192.168.10.2

Based on this command output, what is the operational effect of configuring an OSPF priority of 0 on this interface?

  1. The router is completely excluded from participating in the DR and BDR election process on this multi-access segment.Answer
  2. B
    The router will automatically claim the BDR role if the current BDR goes offline because its Router ID is higher than remaining DROTHER routers.
  3. C
    The router receives top precedence in DR elections because a priority value of 0 represents the highest preferred rank in Cisco IOS.
  4. D
    The interface switches its OSPF network type from Broadcast to Point-to-Point automatically to bypass DR selection.

Answer

Setting the OSPF interface priority to 0 prevents the router from participating in DR/BDR elections on that segment, forcing it into the DROTHER state.
In OSPFv2 broadcast and non-broadcast multi-access networks, setting an interface's OSPF priority to 0 (via the `ip ospf priority 0` interface configuration command) renders that router completely ineligible to be elected as Designated Router (DR) or Backup Designated Router (BDR). The router will strictly maintain the DROTHER state on that segment.

Step-by-Step Solution

1
Examine the output line showing interface priority and OSPF state
The interface displays 'State DROTHER, Priority 0'.
In OSPFv2, interface priority range is 0 to 255, where 1 is the default.
2
Apply the OSPF priority rules for DR/BDR election eligibility
An OSPF interface priority of 0 explicitly designates a router as non-candidate for DR and BDR roles.
Configuring 'ip ospf priority 0' ensures the router never assumes DR or BDR responsibilities, preserving control plane stability on specified nodes.

Key Concept

OSPF Interface Priority and Election Eligibility
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Topics

OSPFv2 Network Types and DR/BDR Selection

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