What is the administrative distance (AD) of OSPF?

• A. 100
• B. 110
• C. 120
• D. 90

Answer: (B)

Administrative distance is the trust level a router assigns to routing information from a particular protocol when multiple sources could provide a route to the same destination. The router prefers the route with the smaller distance.

For OSPF, the typical administrative distance is 110. This makes OSPF routes preferred over those from protocols with higher distances (like RIP at 120) but not as trusted as static routes (1) or directly connected routes (0), or even more trusted internal EIGRP (90). When a destination is reachable via more than one source, the router will pick the route with the lower administrative distance, so 110 is the value used to identify OSPF’s trust level.