Yes, the KMS client activation is supported in multi-domain environment in which the KMS host belongs to one domain and needs to cater to the clients in others.
For this to work, you need to create a ‘multi-string value’ registry key under “HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindows NTCurrentVersionSoftwareProtectionPlatform” called “DNSDomainPublishList” on your KMS Server.
When done, restart the “Software Protection” sppsvc service on your KMS host and watch for the Event ID 12294 log under application logs. You should one event for each domain you have asked KMS to publish itself in.
Additionally, under each domain you can use NSLookup to verify the _vlmcs SRV record.
nslookup -type=srv _vlmcs._tcp
KMS communication happens over TCP Port 1688, if the domains you have added are in other region and you would like to verify if clients can talk to your KMS host, then from a client on the other side use PortQry to ascertain that port is not being blocked
portqry –n FQDN_of_your_host –e 1688 –p both
If the environment does not support Dynamic DNS, then SRV Resource Records can be manually created to publish the KMS host.
The KMS SRV RR is created under TCP node of your DNS Domain.
On how to setup and configure KMS Server/host a Server Core, see my other post.
Other details can be found under Technet Library : http://technet.microsoft.com/en-us/library/ff793419.aspx