With the code in hand, developers learned exactly how to talk to the hardware inside and how to code any features the hardware could support. It has spawning a handful of open source firmware projects for the WRT54G that extend its capabilities, and reliability, far beyond what is expected from a cheap consumer-grade router.

After this little introduction, now the interesting part. Most of the firmwares mentioned above are completely free, you can download any of them from their developer's website, and easily replace your WRT54G firmware, so that you could use the WRT54G as a repeater or a bridge. Create a wireless distribution system (WDS) or a mesh network. Run a VPN server. Or a VoIP server. Or a managed hotspot with a RADIUS server. Manage bandwidth use per protocol. Control traffic shaping. Support IPv6. Boost antenna power. Remotely access router logs. Operate the router as a miniature low-power PC, running a variety of Linux applications.

Besides Linksys’ own official firmware, there are more than a dozen varieties of firmware replacements available for the WRT54G. The most popular are named Alchemy and Talisman, released by a company called Sveasoft, and another named DD-WRT.

Over the years Linksys has released several hardware revisions of the WRT54G, from 1.0 to 5.0 and several point releases in between. What version WRT54G router you have can be determined from its serial number as per charts widely available on the firmware community sites. The serial number is printed on the outside of the box. The reason this matters is because some versions of firmware work only with some versions of WRT54G.

WRT54G firmware come a file with the extension .bin. Regardless of which firmware you choose, be it a Sveasoft release, DD-WRT, or any other, ultimately you are going to have in your possession a .bin file which needs to be uploaded in to the router.

It takes only a few minutes to flash the router with a new firmware, but you must note these key steps.

1. Connect your PC with the .bin file to the router via Ethernet cable. Do not try to flash the firmware through a wireless link, which could be unstable and lead to a brick.
2. Reset your router’s current firmware to factory defaults. You can do this through the current firmware’s configuration pages – Administration/Factory Defaults/Yes/Save Settings. As an alternative, you can physically reset the factory defaults by pressing and holding the reset button on the back of the router for 30 seconds.
3. Now you can flash the new firmware. Connect to the router’s configuration pages with your browser, and navigate to Administration/Firmware Upgrade. Open the browse dialog to select your .bin firmware file.
4. Once you start the firmware upgrade – do nothing! Whistle. Whittle. Have a pint¹. Just don’t touch your computer or the router. Leave them alone for this intimate moment. Hacker interruptus will only produce a new baby brick.
5. After a minute or so you’ll see the upgrade progress bar complete. The router will now reset itself, and assuming everything worked, you’ll see a new page with a button marked Continue.
6. Wait at least two more minutes before clicking the Continue button. Sometimes the router presents the continue screen before it has truly cleaned up from its upgrade, and you’re better safe than sorry. Drink another pint².
7. Now click Continue. You should be forwarded to the main configuration page for your router. In the case of DD-WRT or of Sveasoft Alchemy/Talisman it looks much like Linksys’ own page, except with customized markings and a whole lot more features to explore.

What if you didn’t make it this far? What if something terrible has happened, and the router did not come back to life? This is a rare but possible event. It is very unlikely if you’ve followed steps one through six. Your router may be "bricked", which is somewhat like being dead, except with the possibility of resurrection.

First, try to reset the router to factory defaults by pressing and holding the reset button on its rear for 30 seconds. When and if it relights, try to connect to it with your browser. You may be lucky and have a chance to start the process over again. There are several more tricks you can try to revive a bricked router, also known as recovering from a bad flash. In this case, you want to consult the WRT54G Revival Guide.

Of course, we don't assume any responsibility on the outcome of this little experiment, nor we may not be held responsible for damages direct or indirect that installing a custom firmware on the WRT54G might cause