Building Wireless Community Networks, Second Edition

NAT and DHCP

By default, the AirPort acts as both a NAT server and a DHCP server for your wireless clients.^[11] DHCP service is controlled by the DHCP Functions tab. To turn DHCP on, check the Provide DHCP address delivery to wireless hosts box. You can specify the range of IPs to issue; by default, the AirPort hands out leases between 10.0.1.2 and 10.0.1.50. You can also set a lease time here. The lease time specifies the lifetime (in seconds) of an issued IP address. After this timer expires, the client reconnects to the DHCP server and requests another lease. The default of 0 (or unlimited) is probably fine for most installations, but you may want to set it shorter if you have a large number of clients trying to connect to your AirPort.

If you don’t have another DHCP server on your network, the AirPort can provide service for your wired hosts as well. Check the Distribute addresses on Ethernet port, too box if you want this functionality.

Warning

Check this box only if you don’t have another DHCP server on your network! More than one DHCP server on the same subnet is a bad thing, and will bring the wrath of the sysadmin down upon you. Watching two DHCP servers duke out who gets to serve leases may be fun in your spare time, but can take down an entire network, and leave you wondering where your job went. What were you doing connecting unauthorized gear to the company network, anyway?

If you have more than one AirPort on the same wired network, make sure that you enable DHCP to the ...