I've seen this question asked in different variations, but never in the exact situation I have. I've looked up answers to this for a while now, and I'm leaning towards it not being possible, but here goes:
I have an Airport Extreme base station as my main router. It has the internet connection right from the cable modem and everything works great. I also have a headless Ubuntu box that acts as my file server. This does not have a wireless adapter in it, so my thought was to buy a cheap Netgear router (I got WGR614v10) and configure it as a simple repeater so I can hardwire my server into it. For reasons not important to this discussion *cough*wife doesn't want it upstairs*cough*, my server needs to reside in the basement, and I can't run wire from the Airport down to the server.
So far, I've set up the wireless repeating function on the netgear and put in the MAC address of the airport (although it worked better when I put in the airport ID, not the MAC address). I disabled DHCP on the netgear as well. I set up the Airport with WDS and put the netgear in as a client. I got to the point where the MAC address of the netgear was visible in the Wireless Clients list in the Airport, but that's it. I can't ping that router from the first, and I can't see the server connected to it.
So is what I'm trying to do possible? For those who skipped the above, I want my Airport to wirelessly communicate with my Netgear that has a server connected to it so I can connect to the server while wirelessly connected to my Airport.