How does one add a port forward to an openSSH live connection?

Kenneth Burgener kenneth at
Mon Feb 23 08:32:50 MST 2009

The putty ssh client is an awesome tool.  I also love the fact that 
putty has a Linux, Windows and Mac client, so I can use it from most any 
environment.  One of the features I love is the ability to add a port 
forward from a live connection.  This way I can keep my currently 
forwarded applications running, without having to kill everything then 
reconnect.  Can openSSH add a port forward to a live connection?

I found that I can create the initial port forward with:
  # local forward
  $ ssh [host] -L port:host:hostport
  # remote forward
  $ ssh [host] -R port:host:hostport

Once I have made the connection, is there a way to signal the ssh 
process to add an additional port forward, similar to Putty?

The other feature I found, in Putty, is the "session keep alive" 
feature, which you can also specify time between keep alives.  As far as 
openSSH, I found a "TCPKeepAlive" option, but I am not sure this does 
the same thing as the session keep alive, and I don't see an option to 
specify the time between keep alives.

Thanks you,

More information about the PLUG mailing list