Hi Glenn,
Make sure the KMS client can reach the server by FQDN. If no DNS server is available, add new HOSTS entry to allow IP to FQDN resolution
Open firewall from KMS source clients to the central KMS server on TCP port 1688
What’s more, does the kms server show the incoming request in the event log, and that it is sending a response? Test the port with a telnet connection as outlined in the following link.
http://support.microsoft.com/kb/974998
There is not a duplicate IP anywhere on the network is there? Was the server a clean install or was it from an image? If it was an image could it have a duplicate GUID?
Besides, the KMS server won't start activating licenses until the count reaches 25.
A similar case:
About your question in the last paragraph:
“what is the time frame for kms client to communicate with kms server?”
They have to connect every 180 days. However, the KMS server must have a certain number of activations on it to activate the computer, those activations stored on the KMS server expire every 30 days. Its confusing so an example is in order:
The activation threshold -- essentially how many computers have to activated to the KMS server in the last 30 days -- for workstations is 25. Clients, I think, attempt to reactivate every 7 days. So, if you have more than 25 permantent KMS activated workstations on the same LAN as the KMS server, then a roaming laptop could be out for 180 days at a time. However, if you have less than 25 workstations on the same lan as the server, then a condition could arise where that laptop would not be able to activate if there haven't been 25 'check ins' in the last 30 days.
If you are talking about workstations that will permanently move to another location, then the only way to do it is to create a VPN connection at least every 180 days.
Regards