[Unit]
Description=PPPoE
DefaultDependencies=no
IgnoreOnIsolate=yes
Conflicts=shutdown.target
Requires=network.target
After=network.target
Before=network-online.target

[Service]
Type=oneshot
ExecStart=/usr/syno/sbin/synonet --pppoe-start-all
ExecStop=/usr/syno/sbin/synonet --pppoe-stop-all
RemainAfterExit=yes

[X-Synology]