How to Disable DHCP on a Apple Airport Extreme Base Station
In all their wisdom Apple made it so that if you disable DHCP on the Airport Extreme it also turns off NAT which will break the internet on your network. To get around this issue we have to leave DHCP enabled but only let it assign 2 addresses. Then we tell the router that the 2 addresses are reserved to made up MAC addresses. Bit of a dirty solution and I wish Apple would change this but in the meantime we have no option but to do this.