Turning your DD-WRT device into a real AP

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Jeremiah - Posted on 07 March 2008

Unless you're a home user, you probably expect your wireless access points to simply be a media converter - convert from Ethernet to 802.11x and vice versa. But when you have to deal with consumer grade access points, they usually route as well. This would be fine as long as you could turn this function off easily. But this isn't always the case (the only exception I can think of being the Apple Airports, and even then it's not real clear).

The Linksys WRT54G is a great little device (I have three of them, one of them bricked, another had its wireless chipset fried after allocating too much power to it) that in early incarnations had the ability to update to hacked linux-based firmware. At some point Linksys moved to VxWorks and it got more difficult to run linux on it (if not impossible - I stopped caring when they moved to VxWorks). As a side-note, I went to a talk by the maintainer of the busybox project and uClibc project (Erik Anderson, a Utah native), who told us at the time (pre-VxWorks) Linksys was violating the GPL by using both without providing source.

The stock WRT54G firmware doesn't allow you to turn of the routing functions, at least not that I've found. So the solution is to turn to a hacked, custom firmware like DD-WRT (http://dd-wrt.com). DD-WRT has a host of really cool features, but the one I'm interested in for this post is the ability to turn off most of its functionality and just use it as a media converter. It might be straight-forward to some, but I spend a good hour or so trying to figure it out tonight, so I'm going to post it here.

First (I'm using DD-WRT v23 SP2), under Setup -> Basic Setup, change Connection Type to disabled. Then under Network Setup, put in the IP address you want to give your AP so that you can manage it. Fill in the other details as well. Check the box next to "Assign WAN port to switch", then under "Network Address Server Settings (DHCP)" change it to DHCP Forwarder. Save it, and you're done. You've now got a manageable access point that does the job of an access point - no routing, no NAT/PAT, no firewall, just media conversion.

My mistake was making the WAN interface static with the address I wanted to be able to manage it by as the address.