Airport Express and Linksys WRT600N

Hi,
I am trying to extend the range of my Linksys WRT600N router that is connected to my cable modem. The router is in a basement corner. By the time the signal reaches the farthest room - 2nd floor bedroom on the opposite side of the house, my iPad or my MBP cannot get a strong signal. So I thought the Airport Express would help me do that. But while trying to set it up using the Airport software, I tried various options as posted by folks on this forum and others, but have failed. Most of the posts were with a Linksys WRT54G. Wondering if anyone had luck with a WRT600N and extending it with a Airport Express. My understanding is that if I extend the network, the Airport Express becomes a client of the network and does not forward ip's etc - hence I was trying to join a WDS network. To do that I did the following -
1) Hardwired the Airport Express (Cat5) to the LAN port of the Linksys router.
2) Airport detected it - went in through manual settings, "Joined a WDS network"
3) Modified the Wireless tab to reflect the Linksys SSID
4) Tried both WEP and WPA-Personal - results were the same in both cases
5) Entered the MAC address of the Linksys router (2.4Ghz Channel) into the WDS settings.
6) Airport Express gave the green light.
7) Other laptop,desktop etc. could see the AE through wireless setup and could connect, but could not get an IP address forwarded and so all internet connectivity failed.

Any thoughts/ideas on how I could get this to work? Do I have to flash the Linksys router with a DD-WRT Firmware?

Thanks for any advice!

Anyone?

Thanks for your response!
I am actually trying to set this up as a wireless repeater/bridge. So I did what you suggested, but the AE flashes amber if I disconnect the ethernet cable.

The steps I had described above were to try to set this up in a WDS network. With the Linksys router's default firmware, WDS is not possible directly as I understand. So, tried to connect it up directly with the AE and that way tried to "Participate in a WDS network" as in the Airport Utility ver 5.5.1. With that I get a green light on the AE. But when I tried to connect to it from a different location, I don't get a valid IP address forward and so no internet connectivity....

Since then, I flashed the router with DD-WRT build suitable for WRT600N. I assigned the Airport ID of the AE to the WDS Settings within the WRT600n's wireless settings, I assigned the WRT600n's 2.4Ghz wireless MAC to the AE's WDS tab. Everything goes well. Restart everything. Green Light on AE. But when I connect to it, on my MBP, I connects, but I don't get internet connectivity as a different IP is getting forwarded.

At wits end...probably won't work in my situation...

Thanks.

Any thoughts? I am not able to figure out what I am doing wrong...Do I need to get a second Airport Express and direct cable it to the Linksys? Not quite ready to drop another $100 though. What options do I have?

Partial Progress

I was able to get the AE to "Participate in WDS" with all security disabled. As soon as I enabled WPA-Personal on the WRT600N, the AE gave a "WDS Error" (through the status link) although the light was still green on the AE. I will try WEP 128 bit next, but was wondering if anyone else had other ideas/suggestions.

Thanks.

Solved!!!

Finally got it working!

I thought I had gone this route, but something must not have gone right. I will recap my steps, so if anyone else is in the same boat, they might benefit.
1) I reset the AE to default settings. Connected my laptop via ethernet to the AE.
2)Started with no security at all on the dd-wrt. Set up WDS with mac address of the AE as the LAN entry.
3) Fired up Airport Utility and configured the AE to "Participate in WDS".
4) Under Wireless settings, I put the same SSID and Channel as in the dd-wrt. With no security, I was able to connect to the WDS network.
5) Next I enabled WEP security on the dd-wrt. Entered a passphrase and generated the HEX keys.
6) Went into Airport Utility and under the Wireless tab, clicked on Security.
7) With this version of Airport, I could only get WEP Transitional Security Network. This will only take a 13 character password. I did that
8) Rebooted the AE.
9) After it restarted, opened up the AE and in the main menu, under Base station, there is a menu item called Equivalent Network Password. Clicked on that.
10) Copied the password from there (HEX) to key 1 on the dd-wrt wireless security entry.
11) Saved and applied the settings on the dd-wrt.
12) Disconnected the ethernet cable. Moved the AE to a different location.
13) Enjoying WDS with much better signal strength away from the primary router.

Thanks!