Modify Linksys Firmware .bin file?

[Siliconjunkie]

I know this should be possible, but cant find any reference to it anywhere, so I will turn it over to the great minds of TechIMO...

One of the most annoying aspects of Linksys routers is that you are tied to the 192.168.1.0/24 network.

I realize that this works perfectly fine for 99.9% of the users. Myself, I hate it. I prefer to use 10.0.x.x/24 since I have more than one subnet.

I can change the IP on the router to another and straight NAT works fine, but it breaks port forwarding, which is a huge pain for me.

So, my question is...Is it possible to modify the firmware to use a different subnet. I have tried to have a look at the .bin file downloaded from Linksys but cant find anything to read it.

I know there is a distinct possibility that I will kill my router by doing this, but I am willing to give it a go.

Any ideas?

<cheesy news ticker sound>
This just in....
Found some partial but good info here http://lkml.org/archive/2003/6/7/164/

Appears that the image is based on the CramFS filesystem.
So, apparently there is a way to mount this.

I can do step 4, but not sure how to do step 5, I will need some linux help here. After this I SHOULD be able to modify it from there....

[Siliconjunkie]

W00t!

Ok, I mounted it and can see it.

Quite exciting it is!

Ok, lemmie poke around and see what I can break in here. If anyone is interested in seeing this let me know and I will put it somewhere you can SSH to and give you read access to it.

[nukes]

How did you mount it? With the loopback device?

[Siliconjunkie]

Did this first (have no idea what it does)
dd if=binfilename.bin of=test.dump skip=24577c bs=32c

then
mount -t cramfs -o loop test.dump /mnt/linksys

Since I am wayyyy over my head here I am assuming the the -o loop is loopback.

edit- to clarify, I know what dd does, just not sure about the switches exactly. This is the description where I found the info

Once the download is complete, copy the contents of the file from offset 0xC0020 onward into a new file.

[Siliconjunkie]

Since this has really gone a Linux direction I would like to keep the discussion in the other thread: http://www.techimo.com/forum/t73927.html

Once that part get sorted out, I will post the Linksys related info here.

[nukes]

ok, I'm there.

[M_Six]

I don't understand why you're having problems with subnetting. I have two Linksys routers. One is 192.168.1.x and the other is 192.168.2.x. Port forwarding works fine on both.

[Siliconjunkie]

On mine, the first 3 octets are automagically filled in on the port forwarding page. Just has a text box for the last octet.

The one thing I hadnt considered is that it is just text, but underneath it will be whatever the routers IP is.

[M_Six]

Same here, except the first three octets reflect whatever I have the LAN side of the router set to. If I change from 192.168.1.x to 192.168.2.x, the port forward page changes as well.

Do you have the latest firmware installed?

[Siliconjunkie]

Its about a month old. Noticed today that there is a newer one. I was going to flash it, but im not comfortable doing it via wireless so it will have to wait till I decide to go upstairs.