teoma is our friend.
There's a
named.conf parameter called
interface-interval, which specifies how often named should check for new interfaces. The default is 60 minutes, which is probably too long for it to find
pppx0 if you're testing it right away. You could try setting it to 1 minute and see if it finds the interface. If that works, you could adjust it a bit longer if that wouldn't be too inconvenient in actual use.