Which command is used to verify OSPF neighbor adjacencies on a router?

The command "show ip ospf neighbor" is utilized to verify OSPF (Open Shortest Path First) neighbor adjacencies on a router. This command provides detailed information about the OSPF neighbors, including the state of each neighbor relationship, the router IDs of the neighbors, and other relevant statistics such as the OSPF priority and timers. This is crucial for troubleshooting OSPF configurations and ensuring that routers have successfully formed adjacencies with their designated neighbors.

The other options serve different purposes. For example, "show ip interface brief" provides a summary of the router interfaces and their status but does not report OSPF-specific information. "show ip bgp neighbors" is used in the context of BGP (Border Gateway Protocol) to display information about BGP neighbors, which is unrelated to OSPF. Lastly, "show running-config" displays the current configuration of the router, covering all aspects including OSPF configurations, but does not specifically focus on the OSPF neighbor relationships. Thus, for OSPF adjacency verification, the "show ip ospf neighbor" command is the most direct and informative choice.