what's the syntax of vmsvc/deviceconnection

Hi all, I'm in researching of vimsh. While I'm using the command vimsh -n -e "vmsvc/deviceconnection vmid deviceid connect", I find that vimsh -n -e "vmsvc/deviceconnection vmid deviceid disconnect" does work, while vimsh -n -e "vmsvc/deviceconnection vmid deviceid connect" does not   -

  that is to say, while I use vimsh -n -e "vmsvc/deviceconnection vmid deviceid disconnect", I can see the device (such as a virtual NIC) does disconnect from the VM, however, vimsh -n -e "vmsvc/deviceconnection vmid deviceid connect" can not bring the device back to connection. So I wonder if I type the wrong command.

    Any body can give me a clue?

   Thanks.