This value, delivered only via the gmrpFailure notification per the source, explains why a GMRP group registration attempt failed on a port: lackOfResources(1) if the bridge's filtering database ran out of room, or registrationRestricted(2) if Restricted Group Registration (dot1dPortRestrictedGroupRegistration) blocked it. A network administrator reads this alongside dot1dPortLastGroupFailed in the trap to understand whether the failure was a capacity problem or a deliberate security restriction. For example, seeing registrationRestricted(2) confirms the failure was expected behavior from restricted registration rather than a resource exhaustion issue needing hardware attention.