Wireless Ethernet Bridge Project

Recently, at work we needed to setup a remote data backup to back up our important data to a remote location. Should our building burn to the ground we still have a copy of our data. We looked into getting a point to point connection from the local telco companies and other ISP's and wondered if we could do it cheaper ourselves. With my interest in radio technology and Linux, I went home and spent a fair amount of my own time to learn what we could do.

I quickly learned, bandwidth costs, ALOT! I found off the shelf out of the boxes for $1000 or more, some of them required FCC licenses and a learning curve. I also found some wireless ethernet bridge devices for under $100 but the reviews of these devices were not very impressive.

So, I did some digging and found people hacking the Linksys WRT54GL wireless routers into bridges, repeaters, and several other modes. I thought, hey they are cheap, no licensing required, and just a bit of a learning curve to learn. I reloaded the firmware my routers and used Talisman firmware availible here. Getting the bridge to work is a bit tricky, but its doable (About 10 hours worth of playing).
I used these two wireless routers and added two outdoor 19 db flat panel antennas with LMR400 cable and connectors ($240 worth!) from Radio Labs.

A WRT54GL router	Flat panel Antenna

Then I setup two Linux servers with apache, smokeping, and ifgraph to watch the connection on the bridge.

I am happy to report, I was able to pump about 23 mb/s, or 2.8 mB/s of traffic over the bridge. Thats about all I can get over the bridge. Before I hooked up the Linux servers to the bridge, I tested them on 100 mb/s copper and got about 80 mb/s of bandwidth. So I am confident the bridge is the bottleneck and can only handle about 23 mb/s of bandwidth.

Here are some photos of my setup in my backyard for testing

Ethernet Bridge setup #1	Ethernet Bridge setup #2
Looking accross to the ethernet bridge (30 feet, Wow!)	One of my 19 db flat panel antennas
One end of the ethernet bridge, consisting of hacked wireless access point, snmp enabled switch, and a Linux box

Cost Tally:

Everything else I either had laying around the house or was able to borrow from work for this experiment. I hope to put this on two buildings and go a longer distance to see how well this bridge performs. If nothing else, I have proved this can be done!

RESULTS!

I ran the WRT54GL's on two roofs with the antennas, two linux servers, and snmp enabled switches so I could monitor the bandwidth closely. Here is a picture of the setup

Here are some graphs monitoring the bridge. I setup a crontab to haul a 2 gig file over every 30 minutes.