Which CLI command forces a failed OSPF neighbor relationship to reset?

The clear ip ospf neighbor command is the specific and correct command used in ArubaOS-CX to manually reset one or all OSPF neighbor adjacencies. When a neighbor relationship fails or becomes stuck in a state like ExStart or Exchange, this command forces the neighbor state machine to restart. This initiates a new attempt to form a full adjacency without affecting the entire OSPF routing process, making it the targeted tool for resolving neighbor-specific issues.

B. reset ospf This is not a valid command in the ArubaOS-CX command-line interface for managing OSPF processes or neighbor states.
C. ospf restart This is not a valid command. Restarting the entire OSPF process is a more disruptive action accomplished with clear ip ospf process.
D. clear ospf routes This is not a valid command. Clearing routes affects the IP routing table, not the OSPF neighbor adjacency table, which is a prerequisite for route exchange.

ArubaOS-CX 10.12 CLI Reference Guide

Page 1019. The guide details the clear ip ospf neighbor command.

Command: clear ip ospf neighbor [ | ] [vrf ]

Description: "Clears data structures for some or all OSPF neighbors." This directly supports the function of resetting a neighbor relationship.