If you use module autoloading and have PPP as a module, you will need
to add the following to your /etc/modules.conf or /etc/conf.modules:
-/dev/ppp ppp_generic
+alias /dev/ppp ppp_generic
alias char-major-108 ppp_generic
alias tty-ldisc-3 ppp_async
alias tty-ldisc-14 ppp_synctty