Run this image.
docker run -d \
--name xl2tpd --privileged \
-p 500:500/udp -p 4500:4500/udp -p 1701:1701/udp \
-v /data/apps/xl2tpd/chap-secrets:/etc/ppp/chap-secrets \
--restart always \
docker.sqbj.info/xl2tpd-psk:latest-e DOCKER_NET_SUB=... (defaults to 172.18)
-e PSK_passwd=... (defaults to 123)
/data/apps/xl2tpd/chap-secrets
# Secrets for authentication using CHAP
# client server secret IP addresses
test * test *