Apple Airport - Access DHCP from ethernet connection? Is it possible to have a device connected to an Airport Express via the ethernet cable to access the DHCP / sit within the NAT functionality for Internet use?

I have an existing network where a network switch connects to both the cable modem and the Airport Express. This currently works.

I am now trying to add a wired device (an XBox 360) to the switch. All attempts to sit within the Airport's subnet have failed (manual IP setup, tested with various pings, etc). This leads me to the conclusion that all devices receiving DHCP/NAT connectivity must be wirelessly connected.

As the Airport is bridging the connection to the (internet) router, I'd like the XBox sitting within the router. The cable modem has a static IP, which doesn't share well with both the Aiport + XBox trying to use the Internet.

Is there a way to to allow a device connected via ethernet within the subnet / DHCP-controlled zone?

The alternative is to replace it with a wireless router with a built-in switch.

Thanks.
The DHCP works fine for the airport.

If you use ethernet and a static IP address, then you'll have to choose an IP address outside of the DHCP lease range otherwise you can get IP address conflicts.

For example, if your DHCP range is set to 192.168.0.10 through 192.168.0.20 then you can use the IP address ranges 192.168.0.1 - 192.168.0.9 and 192.168.0.21 - 192.168.0.253 for statically assigned IP address.

Hope this helps