Linksys makes a line of cheap, ubiquitous router/firewall boxes well-suited for use on a home DSL or cable connection and popular among Linux hackers. This HOWTO gives hints and tips for managing Linksys routers from a Linux system.
The specific recipes described here are derived from long experience with a BEFSR41, the 4-port router/firewall box. I have also configured a BEFW11S4v2, the 4-port router with 80211b wireless, and the WRT54G, which is the same box with 80211g; I'm currently using a WRT54G. The web interfaces on all these blue boxes are very similar, and most of the advice should generalize.
In late 2004 the Linksys firmware underwent a major upgrade to 2.x (one easy way to spot this is the Cisco logo at the lower right). I haven't seen anything but a WRT54G running the new interface, but I'd be surprised if it weren't running on the BEFSR41 and kin as well. The changes are largely cosmetic. Some problematic features in earlier versions have been removed.
This HOWTO describes Linksys firmware version v2.02.7. At time of writing (January 2005) the current Linksys firmware version is v.3.01.3. I do not recommend upgrading! I've had a report that enabling WEP on this version makes the box unable to talk to a Linux machine over a cable.
Also note that if you go looking for one of these now, be sure to get the WRT54GL — note the L suffix. At Version 5 and up, the vanilla WRT54G is different hardware with less RAM that runs a proprietary VxWorks OS.
You can also view the latest version of this HOWTO on the World Wide Web via the URL http://www.tldp.org/HOWTO/Linksys-Blue-Box-Router-HOWTO.html.
Copyright (c) 2003, Eric S. Raymond.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is located at www.gnu.org/copyleft/fdl.html.
Feel free to mail any questions or comments about this HOWTO to Eric S. Raymond, <esr@snark.thyrsus.com>. But please don't ask me to troubleshoot your general networking problems; if you do, I'll just ignore you.