Make sure you disable the DHCP server on the Linksys. You want to only use it as an Access Point. Let the Westel act as the DHCP server.

How do I do that? It sounds like it would work

First its not a good idea to piggyback your question on someone else's. This can lead to confusion. You should start a new thread. So I've moved your question to its own thread.

That depends on which router you have. You can go into the router configuration and there should be a checkbox for it.

If your router is a linksys, simply login to your router's interface and under setup is your scrolldown for Internet Connection Type (DHCP, Static IP, Telstra Cable, PPOE,PPTP and L2TP)

Right below that is your DHCP Server Setting and it's either enabled or disabled, this is where you want to disable therfore your modem can act as your DHCP Server.

Hope this helps!