If you're using Bill's kit, its already there.

Try doing a 'route flush' before connecting via ppp, IF you want the
ppp link to be the defaultroute!  Thats what I do.  If I don't, I get
errors from the pppd trying to set the default, because theres already
another one defined!  If you don't want that link to provide the default,
you should REMOVE that statement from the options file, and probably
setup some static routes.

I'd like to ask a question regarding PPP myself, and that is, I see
some process fill the link with traffic as soon as I try to do anything
across it (telnet, netstat, anything).  It kills the performance and it
never seems to stop!  I thought it was routed, and I still suspect its
advertising its routes, or whatever it does.  But, I killed it, and it
still persists.  Is the kernel doing this because it sees the two possible
networks (my ethernet and now the network to which I'm connecting)?

I don't see this behavior when connecting to this same service with any
other system using PPP to build the link.  And that includes FreeBSD, 
Linux (various flavors) and even Win95 or NT.  The only one that does
this is NetBSD/mac68k.

Any ideas?

Paul