Linux on Linksys Wi-Fi Routers

The standard WRT54G is a wireless access point (AP). This means that it can talk to wireless clients but not to other wireless access points. The ability to link it to other access points using the Wireless Distribution System (WDS) or to act as a wireless client is available using the wl command.

The Wireless Distribution System is an IEEE specification that allows wireless access points to be chained together in a wide area network. Although there is some performance penalty for doing this, the end result is an extended wireless network with a much greater range than is available using single APs.

In order to link two APs together using WDS, their respective MAC addresses must be known. Log in to each box and run the command wl wds [Mac Addr], using the MAC address of the opposite machine's wireless interface. A new device called wds0.2 then appears on each box and can be assigned an IP address. Once the IP addresses are assigned and routing is set up between the two boxes, you are able to ping one from the other.

Each WDS link results in data traffic doubling within the network. Because 802.11g is half duplex, this halves the network throughput. If the APs are operating at 54MB/s, this is not much of a performance hit if you keep the links to three or fewer.

A simpler form of bridging is to set up one box as a client and have it link to an access point. This is known as an Ethernet bridge, and several products exist specifically for this purpose.

Client mode must be selected in the Linux kernel build menu and compiled in the kernel. Once done, the kernel is built with a Broadcom binary-only module that includes support for both AP and client modes. The command wl ap 0 sets the box to client mode, and wl join [SSID] links it to an access point. If you set routing in the client using the access point's IP address as the default gateway, the client automatically routes to the access point and your bridge becomes active. Multiple AP and client pairs can be set up as an alternative to the WDS method described above.

Linux has worked its way into everything from supercomputers to embedded systems, including the Linksys. The move to Linux is the result of a highest performance vs. lowest cost equation in a highly competitive market. Many similar wireless routers, such as the Belkin F5D7230-4, the Buffalotech WBR-G54 and the ASUS WL-300g and WL-500g, all use Linux in their firmware, and the list expands daily. Unfortunately, none of these companies has complied with GPL requirements and released the source code. Legal issues aside, these products will lag far behind the Linksys open-source products in capabilities and features for some time to come.

Linksys firmware builds containing amazing new features and capabilities appear daily. At the time of this writing, firmware builds for the Linksys WRT54G with support for VPNs, power adjustment, antenna select, client and WDS mode, bandwidth management and a whole lot more are available from multiple sources. The Internet combined with open-source code can change a small SOHO wireless router into a powerful multifunctional device.

One word of caution: using experimental firmware could kill your box and probably violates the Linksys warranty. If you are a casual user and need home or small office access to a wireless network, this definitely is not for you. Use the official Linksys firmware builds instead.

If, however, you are willing to risk your box and experiment with its potential, you may find it is capable of much more than the specifications listed on the product packaging—thanks to the power of Linux and open-source development.

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