This article relates to Cisco TelePresence Advanced Media Gateway 3610.
A. On the OCS Gateway VCS, go to System configuration > DNS. Are there values for the settings Local host name and Domain name?
If both of these are set, the VCS will use these as a fully-qualified domain name (FQDN) in SIP signalling to the OCS server. In order for OCS to be able to use this information, it must be able to perform a DNS lookup on the FQDN.
To rectify this, ensure that the DNS server used by the OCS server contains an entry for the VCS's FQDN.