Okay, here's what I want to do. I have a wireless dsl modem/router on the third floor of my place and I want to put another wireless router on the first floor and connect other computers there without having to run a wire from modem to router. Is is possible? I know the router will work as a switch/hub without using the wan port, but you have to plug a patch cable from the internet source into a lan port. Can I trick it into thinking the wireless port is a lan port?
What you need is an access point that has passthrough. I think that's what it is called. Bascaly the access point, if it is the right kind, can be set up to pickup the signal from another access point or router and amplify it. Netgear is the one i'm most familiar with and works quite well at doing this task. Just do your research to make sure it can do that. I inherited a brand new linsys 802.11g access point because it didn't to the passthrough.
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Airport extreme base station on the third floor, and a ExtendAir omni should do the trick, you can also add a airport express on the first floor as a relay base station if need be, but the extendair is good for 250 feet, and the express is only good for 10 users. http://www.apple.com for the airport and http://www.drbott.com for the extendair.
Those suggestions are all well and good, but I wanted to do it with what I had. It turns out my roommate bought a repeater/access point to fix the problem so I don't have to worry about it anymore. Thanks for the suggestions, though!