24 March 2013

Airport Extreme: How to Disable DHCP while Maintaining NAT

If you run a DHCP server on your network already you might want to use the NAT capability of an Airport Extreme without using the DHCP server functionality. With a bit of fiddling this is possible.

I found the answer thanks to this post:
kair: How to Disable DHCP while Maintaining NA: Apple Support Communities

To guard against link rot the process is essentially:

  • On the DHCP server:
    • Set the IP to a fixed one e.g.
    • Set the DHCP range to cover the majority of your network e.g. 1-252
    • Set the forwarding DNS servers to an external one e.g. OpenDNS
  • On the Airport Extreme:
    • Ensure it is set to a specific IP e.g.
    • DHCP to a limited range e.g. 253-254
    • On the Internet tab set the DNS servers:
      • To the local DHCP server e.g.
      • I like to set the other one to OpenDNS server to guard against downtime

From the link and using a Windows 2008 as a DNS server the bit I struggled with was "Be sure to specify the Airport Extreme (e.g. as the default gateway or default router". In Windows Server 2008 this is under Server Manager, Roles, DHCP Server, [server name], Scope, Scope Options, right click, Configure Options. The option was greyed out for me until I de-authorised and re-authorised the Scope for some reason (and a customary reboot of course!).

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