apt install openfortivpn

/etc/openfortivpn/myconnection.conf

  host = 1.2.3.4
  port = 10443
  username = test
  password = pass
  trusted-cert = 4114afe52e931c7f50984567ffc390f529ccd668f01b35eff311abc0d052234a

/etc/systemd/system/myconnection.service

[Unit]
Description=OpenFortiVPN for myconnection
After=network-online.target
Documentation=man:openfortivpn(1)

[Service]
Type=simple
PrivateTmp=true
ExecStart=/usr/bin/openfortivpn -c /etc/openfortivpn/myconnection.conf
OOMScoreAdjust=-100
Restart=on-failure
RestartSec=120s

[Install]
WantedBy=multi-user.target

Пингуем через VPN каждую минуту, иначе через 5 минут PPP отваливается сам

/etc/crontab

* * * * * root ping -c 1 192.168.1.100 &> /dev/null

systemctl enable myconnection.service --now