The laptop will update its IP address on sync, alternativly the current version of SBAdmin uses the netbios name OR IP address to communicate with the machine. Finally, you can overwrite the ip address in the machine config with the machines DNS name,
The original question is a bit vague. Are you talking about DHCP or RAS connection? Are you trying to get the machine to synch every time it gets an IP address? If that is the case, just set a initial synch delay of 2 minutes (in case they need to VPN connect first) and then a synch interval of 30 minutes. The more often you synch, the larger your log files get and more open connections will be made to the server. We have about 6000 machines and we use 90 minutes for our synch interval.
As a product enhancement, it would be nice if there were a feature to synch on login, logoff, or ethernet interface link up.
I agree on the feature requests. In the mean time, here's a tip to get more synchs. In the Machine Properties, look in the Synch tab. The option "Resynchronize when RAS connection is detected" is unchecked by default. RAS is pretty rare these days, but many VPN apps look like a RAS connection to Windows. So if you check this box, we will often sync when a VPN connection is established. This depends on the VPN software, but we have good feedback from other customers on this one.
Also, you can setup a boot synch delay to increase your chances of a synch on bootup. Many times the synch attempt happens before the client can get an IP address so it just fails. If you delay it 15-30 minutes, you've got a better chance of being connected when the first synch attempt occurs.