I have succeeded recently to create a WDS link between the two 3Com routers I had around, and I thought I might share the experience with you guys, as it took me a while to get this to work.
The first router I bought a couple of years ago was in fact a 3Com OfficeConnect ADSL router (3CRWDR100A-72), and obviously I got it because I had an ADSL connection at the time. One thing that I liked was that it supported WDS, although I didn't have a use for it righ away, I thought it might come handy someday (and you will see, it did :-)
Last year we moved in our own house and one thing I was looking forward to was to get NTL internet cable, available in the area. Since the old router wasn't going to work with the cable, I bought another one, and I did go for a 3Com again, the OfficeConnect Wireless 11g DSL/Cable Router (3CRWE554G72T). Again, the new router had support for WDS, and it looked like a nice feature to have, as I was thinking that I could connect the two of them if needed.
As I had setup my desktop computer in the small bedroom upstairs, now converted to my own office (yeah!), I asked the cable guys to set up the connection up there as I wanted to have low pings on the net for some online gaming. My wife's Vaio notebook would connect wirelessly from anywhere around the house, so the whole setup made sense.
Recently we've managed to furnish the living room downstairs, and now I could finally bring the TV and the Xbox downstairs, but the question was how to connect the Xbox to the Internet. I looked around for a wireless gateway to be able to connect the Xbox to the wireless router, but I haven't found one for a good price, and then I remembered about my old ADSL router lying around...
As this was an ADSL router, I didn't have high hopes for it, as I was worried that the router would only know to route packages through the dynamic routes created when it connected to the PPPoE server through ADSL. I read up a few articles on the Internet, and the first attempt failed miserably, later on realizing that I was trying to use WPA encryption on both routers, as they were configured when they were used on their own.
I dropped the idea for a while, and decided to get one (or even two) of the new 3Com routers that claim to support WPA over WDS links. I read some more, and I decided to give it another shot, this time starting with no encryption. As one of the articles suggested, I got my 8-port ethernet hub from the old stuff (but always useful ;-) pile, and wire in the two routers and the desktop.
I started by disabling the DHCP servers on both routers, set-up static IPs on the routers as well as on the desktop, to avoid any issues involving DHCP - all IPs were in the same private class (10.xx.xx.xx). I also disabled the NAT support from the ADSL router, as the NATing was going to be performed by the cable router. I configured the routers to use the same wireless channel (the SSIDs do not have to be the same), enabled WDS support, configured the MACs for WDS on both routers and as soon as I saved the configuration, the lights on the hub started blinking quickly, as one of the articles said it would happen, because the packets were going in a loop from the wired connection, through the wireless, and then back through the wired connection. Hurray, there was hope that all the work wasn't in vain!!! I re-configured the routers to use WEP-128 encryption, lights blinking happily, even better news! Tried it once just for the sake of it with WPA-PSK, no sign of life, but I felt happy enough to go back to WEP and try the hole again, this time from downstairs. I decided to stick with the static IPs, plugged-in the Xbox, set the IP and voila, Internet through the wireless WDS link! Now after the couple of hours spent researching, trying, failing and then trying again, we finally deserved a nice long sleep :-)