Are you Gentoo, Red Hat, Debian, SuSe...
In other words, what flavor of Linux are you wanting to enable the interface at boot up?
For Gentoo:
ln -s net.lo net.rausb0
rc-update add net.rausb0 default
rc-update -s | grep net
-fins-
For Debian:
ifconfig - and look for rausb0
if not, try
ifconfig rausb0 up
If successful:
vi /etc/network/interfaces
and added the line:
auto rasusb0
I know Gentoo and *BSD, but Debian is the result of
http://www.google.com...
Good Luck,
Neo