HOW-TO: Greyhat WiFi repeater
posted Aug 23rd 2005 9:30am by Eliotfiled under: Uncategorized
This how-to gives the steps needed to put together a simple man-in-the-middle wireless repeater. You can use this to hang your wired network off of someone else’s wireless router and serve their wireless connection back to them. Do not do this. It here as a silly geek trick and will probably just annoy you every time your connection goes down because you’re too cheap to pay for a good wired connection.
This involves three wireless routers:
Your neighbor is in possession of router A. It is set to factory defaults initially. This is important because it shows the victim isn’t technically savvy and won’t notice your intrusion. You have router B, a Linksys WRT54G that you will be putting into client mode and connecting to router A. The final component, router C, is plugged into router B and acts as a wireless access point.
To start you need to upgrade the firmware on router B so you can use client mode. Follow the client mode HOW-TO over at Engadget.
After that you need to scan for a victim access point. Linksys, D-Link, and Netgear make most consumer routers you’ll find so if you see an SSID of “linksys”, “default”, or “NETGEAR” it is most likely set to factory defaults. This is router A. Connect to the router and go to the default IP address in you web browser, usually “192.168.1.1″ or “192.168.0.1″. The Phenoelit Crew maintains a huge list of default admin passwords. Use the admin interface to change the default local IP to a different subnet like “192.168.2.1″. You’ll have to get a new IP after this. Reconnect to the router and give it a new SSID and admin password. You might as well set up WEP while you’re at it since you’ve commited to being an ass. You need to be careful during this process since you could very easily lock yourself out of the box and without physical access you won’t be able to do a hard reset.
Now that router A is set up we can move onto router B. If you followed the client mode how-to exactly you will have to switch the local IP back to “192.168.1.1″ or whatever router A originally had as a local IP. Also set the default gateway to the new local IP of router A. Configure client mode to connect to router A‘s SSID and then set up WEP.
You are now connected to router B through a wired connection and it is connected to router A wirelessly. You should have internet access.
Now for the final step; giving your neighbor his wireless access back. Plug into router C and go to the admin page. Turn off the dhcp server and change the local IP to one in the subnet, something like “192.168.1.10″. Change the SSID to router A‘s original i.e. “linksys”. Now plug a cable into one of router B‘s LAN ports and the other end into the uplink port on router C; if it is a Linksys router, port 4 will work. Router C is now rebroadcasting the wireless connection.
When your neighbor fires up his wireless laptop it will still say he is connected to “linksys”, but your wired network is “securely” connected to the internet. You could always uplink to another router and set it up as a secure access point.
Once again: do not do this. If you are looking to legitimately expand your wireless coverage with WRT54Gs, you should investigate mesh networking with WDS. It may not work with WPA though.
I do something similar. I wanted my own private network behind my landlords wireless network, so i got a wifi bridge, plugged that into the wan port of my (wifi, but doesnt need to be) router, and im rebroadcasting his wifi signal on my floor. Better connection in random places in my apartment