HowTo reset/enter a Linksys WRT54GL without knowing its IP

[^rooker]

I've just found my old Linksys WRT54GL router which I, years ago, flashed to FreiFunk firmware (v1.2.5) to use it as a FunkFeuer node.
Now, I'd like to use it for its original purpose again: A wireless router.

But, I've played around with the FreiFunk configuration a lot, and it was faaaaaar away from default settings - and years ago - so I did not know how to "find" my WRT54GL in my network.

a) First guess: Try DHCP!
Yeah, right.
If DHCP would have been activated, I would not write this HowTo.

b) OpenWRT failsafe mode:
That one is great!
FunkFeuer is based on OpenWRT, and therefore also has the failsafe mode.

Here's how:
1) Turn the router off. Unplug the power.
2) connect any LAN port of the router directly to the network card of your PC
3) Assign any 192.168.1.x IP address to your PC (e.g. 192.168.1.5)
4) During startup of the router device, OpenWRT tells you when to press the reset button to enter the failsafe mode. You just have to "listen":

Code: Select all

tcpdump -i eth0 -n -A host 192.168.1.1

5) Now power on the router (and prepare to press the reset button on the back)
6) After a few seconds, tcpdump will spit out a message like this:

15:47:13.862070 IP 192.168.1.1.2048 > 192.168.1.255.4919: UDP, length 1001
E.....@.@..............7...+..Press reset now, to enter Failsafe!.................

7) Press "reset" on the back of the router
telnet to 192.168.1.1, and you'll get a nice welcome shell prompt like this:

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telnet 192.168.1.1

Trying 192.168.1.1...
Connected to 192.168.1.1.
Escape character is '^]'.

BusyBox v1.01 (2006.04.12-12:05+0000) Built-in shell (ash)
Enter 'help' for a list of built-in commands.

_______ ________ __
( ).-----.-----.-----.) ) ) ).----.) )
( - )) _ ) -__) )) ) ) )) _)) _)
(_______)) __)_____)__)__))________))__) )____)
)__) F R E I F U N K F I R M W A R E

@bmpbox:/#

[^rooker]

On the FreiFunk wiki, they have a nice HowTo about how to deal with your router in case of a broken firmware update. My router's firmware wasn't broken, but I wanted to change the firmware to regular "OpenWRT".

Why am I posting a thread about this?
Because FreiFunk's web-interface for updating the firmware was slightly confusing me:

If you open the FreiFunk web interface and select the menu option "firmware" on the left side, you don't get any upload form, but some message displaying which partitions are mounted, blablabla...

Long story short:
There is a link to a "restart" page of the web-interface, where you must select to reboot the router and start it in one of the following modes:

• failsafe mode
• failsafe mode (read-only)

After the router has restarted, open the FreiFunk webinterface again, open the "firmware" link - and voila: You get a regular firmware upload form.
You can upload either a .bin file, or a .trx - it can handle both.


More information can be found on the FreiFunk website about the WRT54(G/GL/GS) device.