An rlOspfv3NbrStateChange notification signifies that there has been a change in the state of a non-virtual OSPFv3 neighbor. This notification should be generated when the neighbor state regresses (e.g., goes from Attempt or Full to 1-Way or Down) or progresses to a terminal state (e.g., 2-Way or Full). When a neighbor transitions from or to Full on non-broadcast multi-access and broadcast networks, the notification should be generated by the Designated Router. A Designated Router transitioning to Down will be noted by ospfIfStateChange.
Sources for this description
Multiple manufacturers; see the original MIB MIB copies (LibreNMS/Observium Community)NETGEAR official product and EOL MIB downloads