Most access point hardware includes a built-in DHCP server to automatically allocate IP addresses to your wireless clients. In many cases, this range is the same as the range used for other Internet-sharing services, such as Windows ICS. Because of this, you’ll need to be careful of conflicts, since multiple devices (including other access points) may be handing out duplicate IP addresses on your network. Be sure to limit DHCP functionality to a single device by disabling the service on either your access point or other internal servers. If you’re using ICS to share an Internet connection, the DHCP component cannot be disabled, so keep this in mind.
Some folks recommend changing the IP address range used by your DHCP server if possible. Most access points will hand out addresses in the 192.168.0.x range, another well-known fact. Unfortunately, simply disabling DHCP will not solve the problem, since rogue users will commonly configure themselves with a static address in this range as an educated guess. To combat this issue, consider changing the gateway IP address of your access point from the default value (typically 192.168.0.1), and use static addressing for wireless clients instead. If anything, this will make things harder to guess, but realize that anyone using a packet capture utility on a network not using WEP or WPA would still be able to determine the range in use with relative ease via a utility like AirSnort. This is just another reason why implementing MAC address security is critical as a method of limiting which systems can connect to your network.