You need to change the ServerAliveInterval, as explained in ssh_config(5):
Sets a timeout interval in seconds after which if no data has been received from the server, ssh will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server.
For example, create
~/.ssh/config and add:
Host * ServerAliveInterval 120
This will apply to all connections. For a single connection, just use the -o option as explained in ssh(1):
ssh -o ServerAliveInterval=120 user@host