First, check that you've got a default route. By running http://www.freebsd.org/cgi/man.cgi?netstat name="netstat -rn">, you should see two entries like this:
Destination Gateway Flags Refs Use Netif Expire default 10.0.0.2 UGSc 0 0 tun0 10.0.0.2 10.0.0.1 UH 0 0 tun0
This is assuming that you've used the addresses from the
handbook, the man page or from the ppp.conf.sample file.
If you haven't got a default route, it may be because you're
running an old version of ppp that doesn't understand the
word HISADDR
in the ppp.conf file. If your version of
ppp is from before FreeBSD 2.2.5, change the
add 0 0 HISADDR
line to one saying
add 0 0 10.0.0.2
Another reason for the default route line being missing is that
you have mistakenly set up a default router in your
/etc/rc.conf file (this file was called
/etc/sysconfig
prior to release 2.2.2), and you have
omitted the line saying
delete ALL
from ppp.conf
. If this is the case, go back to the
Final system configuration section of the handbook.