How to umount

Can anyone show me how to solve this problem.
I mounted with this command:
#io-pkt-v4-hc -d msk -p tcpip

Now I want to umount this module.
First i do:
ifconfig msk0 down.

But after that I can’t use
#io-pkt-v4-hc -d msk -p tcpip
to mount Can anyone tell me what wrong with this umount command.

Many thanks.

I can’t use ifconfig msk0 destroy? Why?