Systemd/test/test-network/conf/25-fou-gretap.netdev

[NetDev]
Name=gretap96
Kind=gretap

[Tunnel]
Local=10.65.223.238
Remote=10.65.223.239
Key=1.2.5.106
SerializeTunneledPackets=true
Independent=true

FooOverUDP=yes
FOUDestinationPort=55556