mounting driver on /dev/io-net/en1

Here are the command i am using
$ io-net &
$ mount -Tio-net -overbose devn-mydriver.so
$ mount -Tio-net -oif=en0:11.2 npm-ttcpip.so

This command mounting it on a /dev/io-net/en0…
but I want to mount it on en1…

What will be the command line option to mount it on
/dev/io-net/en1 ???

Umesh