Keep Alive SSH Sessions

To enable the keep alive system-wide (root access required), edit /etc/ssh/ssh_config;
to set the settings for just your user, edit ~/.ssh/config (create the file if it doesn’t exist). Insert the following:

Host *
    ServerAliveInterval 300
    ServerAliveCountMax 2

You can also make your OpenSSH server keep alive all connections with clients by adding the following to /etc/ssh/sshd_config:

ClientAliveInterval 300
ClientAliveCountMax 2

References
https://patrickmn.com/aside/how-to-keep-alive-ssh-sessions/