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

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 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.