Answer by Stephen Quan for SSH remote port forwarding failed

For me when a ssh tunnel disconnects it takes awhile for the connection to reset so the ssh process continues to block leaving me with no active tunnels and I don't know why. A workaround solution is to put ssh into the background with -f and to spawn new connections without waiting for old connections to reset. The -o ExitOnForwardFailure=yes can be used to limt the number of new processes. The -o ServerAliveInterval=60 improves the reliability of your current connection.

You can repeat the ssh command frequently, say, in a cron, or, in a loop in your script, for example, in the following, we run the ssh command every 3 minutes:

while (1)
do
    ssh -f user@hostname -Rport:host:hostport -N -o ExitOnForwardFailure=yes -o ServerAliveInterval=60
    sleep 180
done