SSH keep-alive interval...

Adjustiing the ssh keepalive interval down is an essential part of traversing nat translation and stateful inspection devices that reap stale or idle connections...

There are basically three place this parameter can be tuned.

in the sshd_config (to adjust on the server daemon)

ClientAliveInterval 30

in the ssh_config (to adjust for the client on a system-wide basis)

ServerAliveInterval 30

or in the user's ~/.ssh/config file (to adjust just for yourself)

ServerAliveInterval 30

what's the right interval?

I'm persistently afraid of timers with a 60 second interval so I aimed to get below that. A proper approach would be 3x the number of keep-alives as the theoretical timer (60s) but 30s is still about 86400 packets a month just to keep this session alive so increasing the frequency if this works is somewhat wasteful.