Create SSH VPN over PPP
sudo vi /lib/systemd/system/pppd.service
[Unit]
Description=PPP over Serial link
After=network.target
[Service]
ExecStart=/usr/sbin/pppd nodetach noauth silent nodeflate pty "/usr/bin/ssh root@<your_remote_server_ip> /usr/sbin/pppd nodetach notty noauth" ipparam vpn 172.18.8.1:172.18.8.2
Restart=on-failure
[Install]
WantedBy=multi-user.target
sudo systemctl reload pppd