CCNA: Cisco Certified Network Associate — Question 331

What is the effect when loopback interfaces and the configured router ID are absent during the OSPF Process configuration?

Answer options

• A. The lowest IP address is incremented by 1 and selected as the router ID.
• B. The router ID 0.0.0.0 is selected and placed in the OSPF process.
• C. No router ID is set, and the OSPF protocol does not run.
• D. The highest up/up physical interface IP address is selected as the router ID.

Correct answer: D

Explanation

When loopback interfaces and a configured router ID are not present, OSPF selects the highest up/up physical interface IP address as the router ID. Options A and B are incorrect as they describe different behaviors that do not occur in this scenario, and option C is wrong because OSPF will still function by selecting the highest IP address.