If you are an AT&T/former Bellsouth DSL customer using PPPoE on pfSense, a recent change made by AT&T has broken the pfSense PPPoE client in its default configuration for some customers. This change seems to be getting rolled out almost at random, affecting different people at different times. m0n0wall is affected in the same fashion, with the same resolution.
The fix is to backup your configuration (Diagnostics -> Backup/Restore), open it in a text editor and go down to where you see <pppoe>. Add a line somewhere between <pppoe> and </pppoe> containing only <dnsnosec/>. So a portion of your configuration will look like the following:
Then save the configuration, go back to the Backup/Restore page and restore the modified configuration. The PPPoE client will begin immediately working again.
Thorough discussion of the issue if you’re interested – AT&T’s Random DSL Configuration Changes Begin.