Refer to the exhibit. Given the output for this command, if the router ID has not been manually set, what router ID will OSPF use for this router?

The correct answer is C. 172.16.5.1. OSPF selects the router ID using this priority order (when not manually configured): (1) Highest IP address on any loopback interface, (2) Highest IP address on any active physical interface. Loopback interfaces are always preferred because they are logical, never go down, and pr

Implement a Scalable OSPF Based Solution

Question

Refer to the exhibit. Given the output for this command, if the router ID has not been manually set, what router ID will OSPF use for this router?

Options

A10.1.1.2
B10.154.154.1
C172.16.5.1
D192.168.5.3

How the community answered

(58 responses)

A
3% (2)
B
12% (7)
C
79% (46)
D
5% (3)

Explanation

OSPF selects the router ID using this priority order (when not manually configured): (1) Highest IP address on any loopback interface, (2) Highest IP address on any active physical interface. Loopback interfaces are always preferred because they are logical, never go down, and provide a stable identifier. In this scenario, 172.16.5.1 is the highest IP address assigned to a loopback interface on the router, so OSPF selects it as the router ID. Physical interface addresses (like 10.1.1.2, 10.154.154.1, 192.168.5.3) are only considered if no loopback exists.

Topics

#OSPF router ID#loopback interface#interface selection#OSPF configuration

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