Yea, you can enter the IP address,Subnet Mask, DG,DNS all manually, but nothing beats DHCP. You can either choose to use the ISP DNS or your server IP address. The only difference is that the client will look to your server, then the server if it doesn't know how to resolve the address will contact your ISP DNS server. Then your server will cache that site for future use, which in turn builds up it's database so it's great to have a DNS server running on your LAN. Anyways you still need DNS for active directory so it wouldn't matter.