If there is no entry in the cgkZoneSubnetTable matching the
subnet of the GRQ originator, then the gatekeeper uses the
value of this object for determining the response.
The description of the value is:
enable Gatekeeper response to a GRQ/LRQ is GCF/LCF if
the GRQ/LRQ has a matching or NULL
gatekeeperIdentifier.
disable Gatekeeper does not respond if the gatekeeper
identifier in the GRQ/LRQ doesn't match.