(For some models you can use ddadder program.... http://www.dd-wrt.com/phpBB2/viewtopic.php?t=12166)

Normally, most companies let you upload firmware directly from the user interface. Buffalo unfortunately encrypts their firmware, and they'll only accept encrypted firmware in their web interface. So the easiest way to replace the firmware turns out to be the same way you would "de-brick" a router with corrupt firmware.

Namely, all the broadcom routers enter a special mode in the first few seconds after power is applied that allows a tftp transfer to directly program the flash rom with new firmware. So what you need to do is get everything ready to go, power up the router, and then send it the new firmware quickly.

It turns out to be easier then it sounds.

Gotchas: The special mode uses the default IP address of the router. So if you've changed the ip address of the router since you got it you need to set everything up on the old IP address not the new one. You also need to do this with a wired connection, not a wireless connection. This means that you need to give yourself a static IP address on the wired network (i.e. set your computer to use 192.168.11.2 instead of using DHCP).

Use only v23 SP1 final or later. Older releases may cause trouble!

TFTP Flashing Buffalo Routers under Windows

1. For thoroughness, reset to factory defaults by holding the reset button while plugging in the router. Hold for at least 30 seconds. Unplug the router.
2. Connect your computer directly to one of the LAN ports on the router. (You can use a regular cable or crossover).
3. Because the Buffalo starts up with 192.168.11.1(or 192.168.12.1 for WZR-RS-G54), your computer's IP needs to be in the 192.168.11.0/24 subnet (e.g. 192.168.11.2, mask 255.255.255.0 or 192.168.12.2, mask 255.255.255.0 for WZR-RS-G54). It CANNOT be set to 192.168.11.1 as in the picture below, because it will conflict with the router. You will have to set a static IP. A static IP is critical for the tftp procedure to work; a dynamic IP won't work even if the dynamic IP is currently set in the proper subnet. For Windows XP, the following screen shots should help. After selecting "Internet Protocol (TCP/IP)," click on the Properties button to open the next screen. Enter the info as shown and click 'OK'. Leave Default Gateway blank.

 Open a command window. Go to Start->Run->"cmd".

1. Change your directory to the folder containing the firmware image. (Ex. cd "C:\Documents and Settings\All Users\Desktop" (if you saved the .bin file to the Desktop)
2. Type tftp -i 192.168.11.1 PUT (file name of firmware image) like: tftp -i 192.168.11.1 PUT dd-wrt.v23_generic.bin. (For WZR-RS-G54 use 192.168.12.1 as the router IP.) Do not press enter yet.
3. There are a few methods for this step that might work:
   • Grab the power cable to the router (should be unplugged). Now, hit Enter to start the TFTP transfer and immediately connect the power to the Buffalo.
   • On some systems the order above appears to be incorrect. It worked in Windows XP if, while monitoring the properties tab of Network Places, you hit Enter right after Windows shows connected on the net adapter you are using. You may continue to get TFTP transfer "timed out"s unless you wait for port to connect first.
   • Some people have found that they have better luck if you plug in the power cable for the router first, then wait a few seconds until you see the red "DIAG" light come on the front of the router. As soon as you see that, you'll want to press Enter to immediately start the TFTP transfer.
4. All port LEDs will illuminate.
5. The LED on the LAN port will flash rapidly for about 6 seconds. The command will complete with a success printout, like Transfer successful: 3502080 bytes in 5 seconds, 700416 bytes/s
6. The router will reboot and then boot DD-WRT, wait until the bridge/diagnostic light turns off.
7. At this point, the router is ready to use. There is no need to reboot it (unplug/plug), although this is a safe precaution.
8. The router will be now be accessible on 192.168.1.1 netmask 255.255.255.0. You will need to change your IP to this range to access it for configuration. In other words, change your static IP from 192.168.11.2 to 192.168.1.2. (For the WB2-G54, the router is still accessible at 192.168.11.1).
9. The username is 'root' and the password is 'admin'.

Unplugging router can cause media detect network cards to show no media, ie "Network cable disconnected." When you start the tftp and plug the router in, the NIC doesn't detect media until after the tftp flash window has passed, so 60 seconds later the tftp times out and the router boots normally. If so, don't unplug the router. Get your tftp ready, hold down the Init (Reset) button on the router, with the Init held down and the Diag blinking, start tftp and immediately release the Init button. You'll never get the 'Cable Disconnected' errors, and it should flash right up.

***If you are still having trouble with timeouts, etc., you may want to try using the TFTP client from Linksys (ftp://ftp.linksys.com/pub/network/tftp.exe). Be sure to set it to retry at least three (3) times. Five (5) would be a safe number to start with.***