Create systemd service file.

sudo vim /etc/systemd/system/<service>-tunnel.service

Edit file /etc/systemd/system/<service>-tunnel.service (example, tunnel port 9200).

[Unit]
Description=Persistent SSH Tunnel
After=network.target

[Service]
Restart=on-failure
RestartSec=5
ExecStart=/usr/bin/ssh -NTC -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -o StrictHostKeyChecking=no -L 9200:127.0.0.1:9200 user@192.168.1.100 -i /home/some/.ssh/some.id_rsa

[Install]
WantedBy=multi-user.target

Enable & daemon reload systemd.

sudo systemctl daemon-reload
sudo systemctl enable <service>-tunnel.service
sudo systemctl start <service>-tunnel.service