Symptom
If you are connected to the Internet with PPPoE and try to turn on AppleTalk at the same time, a message appears in the AppleTalk pane that says:
"AppleTalk cannot be used with PPPoE. To use AppleTalk, select the Advanced pane and create a new Ethernet configuration."
Note: This does not affect your computer in two circumstances.
1. Your computer connects to an AirPort Base Station or other router that has already made the actual PPPoE connection. Your computer is not in a direct PPPoE connection, so you should not have selected the PPPoE checkbox.
2. You enable AppleTalk and PPPoE on two different network interfaces, such as AirPort and Ethernet.
Solution
You can create multiple configurations of the Ethernet port to allow access to AppleTalk.
Follow these steps:
1. Choose System Preferences from the Apple menu.
2. Click Network.
3. If you are not logged in to Mac OS X as an Admin user, click the padlock to enter an Admin user name and password.
4. Choose Active Network Ports from the Show pop-up menu.
Note: Some names have changed. For versions prior to Mac OS X 10.1, choose Advanced from the Configure pop-up menu.
5. Click Built-in Ethernet to select it.
6. Click Duplicate.
7. Rename the new port configuration, if desired, then click OK.
8. Choose the name of the port configuration you just created/named from the Show pop-up menu.
9. Click the PPPoE tab.
10. Deselect "Connect using PPPoE".
11. Click the AppleTalk tab.
12. Click the checkbox to select Make AppleTalk Active.
13. Click Save.