So, after wrestling with it for a few hours, my suggestions are
- Connect your Mac directly to the Motorola cable modem and make sure you can connect. Note that you’ll need a copy of Launch! or something to give Telstra the heartbeat
- Tell Launch to disconnect. This will log your user out of Telstra’s network. If you don’t do this much pain will ensue as the network won’t let you in if it still thinks you’re currently logged in.
- Get your Mac’s MAC address from the Network control panel or by using ifconfig on the commandline in the Terminal
- Turn on your Linksys, plug the Mac into it (or connect via wireless) and connect to it using your web browser, typically at http://192.168.1.1/
- Tell the Linksys to masquerade its MAC address as the same as your laptop. This is in case the Motorola cable modem bonds to your Linksys address
- Save the Linksys settings
- Turn off the cable modem
- Connect the Linksys to the Cable Modem
- Turn off the Linksys
- Turn on the cable modem
- Cross fingers
- Turn on the Linksys
- Attempt to connect to the net and browse a page from your Mac. It should have been assigned an IP number such as 192.168.1.100 or somesuch via DHCP, and it should be able to connect.