Side note: If you want to know if your WRT310N is a v1 or v2, flip it over and look at the serial number on the label:
- If the serial starts with "CSF0", then it's a v1
- If the serial starts with "CSF1", then it's a v2
Weirdly enough, the TomatoUSB website doesn't really have any installation instructions except for one ASUS model, but here's what worked for me:
1. Download a supported build from the Download page. The site indicates only the Kernel 2.4 versions are compatible, so I picked the "NoUSB Std" build of the Kernel 2.4 version.
2. Extract TRX file from the RAR file you downloaded. You'll need an archiving utility like 7-Zip to open the RAR file.
3. Change the extension of the TRX file to BIN. So if it was named "tomato-blah-blah.trx" before, it will say "tomato-blah-blah.bin" after. Windows will warn you about changing the extension, but it's fine.
4. Make sure your PC is connected to the router over a wired connection, then log into the Linksys web interface.
5. Go to the Administration tab, then select Firmware Upgrade. Select the BIN file you just renamed, and then upload it to your router.
6. Wait for it to restart, then try to connect to your router again in your web browser. The IP address of your router is now 192.168.1.1 (it might not have been before) and the username and password are admin/admin.
7. You should now be in the Tomato interface! Now that you're in, you'll want to nuke the NVRAM to clear out any cruft in there. It's under Administration > Configuration > Restore Default Configuration > "Erase all data in NVRAM Memory (thorough)." The router will reset again.
8. Log back in and change your admin password now before you forget. Then muck around and set up the router just the way you like it.