Why does Airport Extreme disable LAN interfaces in client mode?

I have configured my wireless airport extreme to use client mode (hint: if this is not available in "manual configuration", start the assistent and it will appear in the menu ...). This is working fine and I can access APX via my default wireless connection. However, I have a few systems attached to the LAN ports and these are not accessible. I read that the APX is disabling the LAN ports in this configuration (why?) - is that true? Someone knows a way to have this configuration running in bridge (or routed mode, I don't care ...) mode? Thanks a lot sven