In a given place, an AirPort has been connected to the Internet. A Linksys router was added, however, it does not support acting as repeater, however, hidden, there is the ability to act as a WDS master.
The secret is based on the following steps, using the default firmware:
1. Setup Linksys for WEP, setup a key, setup an SSID and a channel.
2. Setup AirPort for WEP, using the same strength, using the same key, same SSID and same channel.
3. Setup AirPort for WDS, acting as “remote base station”. Add the MAC address of the Linksys (I got it using ‘iwlist’ command under Linux, when already connected to it. This is NOT the MAC marked on a sticker at its bottom!)
This should work. Try connecting a client machine to the AirPort Ethernet adapter and renew your DHCP lease to verify it’s working.
Reference taken from this blog. It helped me a lot.