Matt is correct. The easiest way is to tell the router to reserve an IP for a specific MAC address. In this case your voip adapter. This way no matter if you ever reboot the adapter or your entire network; your router will always assign the voip adapter the same IP address. e.g. 192.168.1.40. Then, if you need to do any port forwarding, DMZ, or whatever the reason; you'll be able to do it. It's almost always better to do it this way than to manually assign it inside the actual devices. One of the main reasons is in case you ever buy a new router or you happen to reset one of your devices. Then you'll have a difficult time getting back into it. e.g. Linksys starts their ip addresses with 192.168.1.x but a company like dlink might start with 192.168.0.x. Anyway; Matt gave good advice. Get your router to reserve a specific IP address for the adapter instead of manually configuring the adapter for a static IP.