#The changes you've made in /etc/ssh/ssh_config and /etc/ssh/sshd_config are correct but will still not have any effect.

#To get your configuration working, make these configuration changes on the client:

#/etc/ssh/ssh_config

Host *
ServerAliveInterval 100
ServerAliveInterval The client will send a null packet to the server every 100 seconds to keep the connection alive

#NULL packet Is sent by the server to the client. The same packet is sent by the client to the server. A TCP NULL packet does not contain any controlling flag like SYN, ACK, FIN etc. because the server does not require a reply from the client. The NULL packet is described here: https://www.rfc-editor.org/rfc/rfc6592

#Then configuring the sshd part on the server.

#/etc/ssh/sshd_config

ClientAliveInterval 60
TCPKeepAlive yes
ClientAliveCountMax 10000

#ClientAliveInterval The server will wait 60 seconds before sending a null packet to the client to keep the connection alive

#TCPKeepAlive Is there to ensure that certain firewalls don't drop idle connections.

#ClientAliveCountMax Server will send alive messages to the client even though it has not received any message back from the client.

#Finally restart the ssh server

#service ssh restart or service sshd restart depending on what system you are on.