WRT54G-RG

The Linksys WRT54G-RG router has 54mbps WiFi, 4 100mbps ETH-ports and 0 USB-ports. It also supports custom firmwares like: dd-wrt, OpenWrt

Quick links:
Default password/Login
User Manuals
Flashing Custom Firmwares

WRT54G-RG router specifications (specs)

System specs
CPU: 200 MHz
RAM: 32 MiB
Flash: 8 MiB
Custom firmwares: dd-wrt, OpenWrt

Connectivity
WiFi: 54mbps (bg)
WiFi bands: 2.4GHz
WiFi throughput: n/a
WAN: 1 x 100mbps port
ETH: 4 x 100mbps ports
USB-ports: 0

Hard reset instructions for Linksys WRT54G-RG

If your WRT54G-RG router is not working as it should, dropping connections or not being responsive, you should first do a reset of the router to see if the problems persist. Other scenarios where you might want to reset your router is if you've forgotten the password or misconfigured it and can't get access anymore.
Your can reset your Linksys WRT54G-RG in the following way(s):

Through the web interface

Open your browser and navigate to the router interface (check default settings below)
Under the Administration tab you will find a sub-tab called Factory defaults
On the Factory defaults page click the button labeled Restore Factory Defaults

With the reset button

Have your unit powered on
Press and hold the reset button for at least 10 seconds until the power light starts blinking, then release.
When the power light goes solid, unplug the power to the router for 10 seconds
Plug the power back in and start the router
When the power light goes solid again the router is ready to use.

The 30-30-30 reset

If the above instructions don't work you can always try the 30-30-30 reset as follows:

When router is powered on, press the reset button and hold for 30 seconds. (Use a paper clip or something sharp)
While holding the reset button pressed, unplug the power of the router and hold the reset button for 30 seconds
While still holding the reset button down, turn on the power to the unit again and hold for another 30 seconds.

This process usually works for resetting any router to it's factory setting.

Note: It is worth reading more about how to reset routers with the 30 30 30 reset and what the risks and considerations are when resetting your router this way, instead of just rebooting it.

Default factory settings for Linksys WRT54G-RG

If you have performed a reset of your WRT54G-RG device or not changed the defaults, you should be able to access it with the following settings:

Default Gateway IP: 192.168.1.1 Linksys login instructions
Default password: admin
Default subnet mask: 255.255.255.0
Default DNS server: 192.168.1.1
Note: If you are using the default settings you should change them to increase security and prevent unathorized access to your network.

WRT54G-RG Firmwares

Staying up to date with the latest firmware is a good idea to keep your router even more secure from various security flaws.
If you want to squeeze a little bit of extra functionality out of your router, consider flashing an open-source firmware like dd-wrt, openWRT or LEDE. Flashing a custom ROM can greatly increase the stability and functionality of your old router.
Following are the firmwares that we have identified existing for the Linksys WRT54G-RG:

Flashing dd-wrt on the Linksys WRT54G-RG

Instructions on how to flash dd-wrt onto your Linksys WRT54G-RG can be found on the dd-wrt wiki
Note: Always make sure to read the wiki and howtos of dd-wrt before doing any flashing.

Flashing OpenWrt on the Linksys WRT54G-RG

The Linksys WRT54G-RG is supported by OpenWrt according to their Table of Hardware. So flashing OpenWrt onto it should be quite straigthforward.
To get started with the flashing, head over to the OpenWrt instructions for WRT54G-RG and they'll take it from there.
Note: Flashing custom firmwares is always on you're on own risk. Make sure to read OpenWrt's wikis to understand the risks and how to proceed if something goes wrong.