To get your AP prepared follow the steps on following site: http://wrt-wiki.bsr-clan.de/index.php?title=WRT54G_v4_Installation_Tutorial

Internet Connection Type: DISABLE
Network Setup: Fill in what u need
Network Address Server Settings (DHCP): make sure “DHCP Type” is DHCP Forwarder
Rest: unimportant :)

Make sure every checkbox has it’s mark at the first line (“0”)!
Wireless has to be assigned to “LAN”

“Wireless SSID Broadcast” has to be ENABLED!

“MAC Radius Client” MUST be ENABLED!
“MAC Format” MUST be “aabbcc-ddeeff”!

NEVER EVER try to use RADIUS here!!!!!
Rest as you need it

Frame Burst: Enable
Max Associated Clients: 128 is a bit high… set it to something usefull
AP Isolation: ON
TX Antenna: Right (figured that it works best if set to left or right)
RX Antenna: Left (make sure TX and RX are NEVER the same!!!!)
Xmit Power: something that u just have to try! ATM it is set to 20 mW works fine for a radius of 20 meters inhouse

Leaf the Rest to Default

In this case DISABLED, but u can try it out …

Great Feature, but not tested yet.

DNS Masq: ENABLED
802.1x: VERY IMPORTANT!!!!!!!!! MUST BE ENABLED!!!!!! (otherwise no wireless is available)
Routing: ENABLED
MAC Masquerading: DISABLED

DHCP Daemon: DISABLED
SSHD: ENABLED (very nice feature to play around in the shell)

If you follow these instuctions shurdix and the Linksys AP will work together perfectly!