I have the following in my ~/.ssh/config, which for those who don't know, maintains the connection even after you disconnect so you can reconnect really quickly:

    ControlMaster auto
    ControlPath /tmp/%r@%h:%p
    ControlPersist yes

Having said that, sometimes I need to remove the entry from /tmp to reconnect if my network settings have changed.

  > Having said that, sometimes I need to remove the entry
  > from /tmp to reconnect if my network settings have changed.

You can also just send the exit command to the conn.

  ssh somehost -O exit

In addition, I put my controlpath in my .ssh dir. Keeps it out of the global /tmp dir. shrug

  controlpath  ~/.ssh/cp-%r:%h:%p

Have you used ControlPath with a very long hostname? I haven't worked out how to stop one of my IPv6 hosts failing with that setup - the DNS RR is really long (causes problems with IRC, too!)

Hmm. I have one control file with 44 chars in it. That is probably the longest one I have hit. You could always give it a dns cname alias or something.