Optus do not provide support to set up their DSL with Linux. After lots of trial and error, these are the settings that worked for me. I am not a Linux expert so I can't answer any questions - I just know this works!
Optus supplied the modem and setup CD to make a "user install" arrangement, which worked fine in Windows. When you install using the CD, the modem is programed with all the correct settings. I was able to test the installation on Windows and verify all settings were correct. The set up program installs a task bar icon for quick access to DSL settings (data used, log on, log off etc.) which is useful but not essential.
Select SET UP A NEW NETWORK INTERFACE

Note that you do not set up the Internet in Mandriva Control Center, you only set up the network card to see the modem - the modem takes care of the Internet DSL settings! The only way I could make it work was to use a fixed IP address for the network card.






Press NEXT to complete the setup.


Change the device selected to "unknown (sit0)" and enter the settings below:


If you have problems, I have included copies of config files, which is a more technical way of configuring the network settings.



