clevyr/forticlient repository overview

# Create a docker network, to be able to control addresses
docker network create --subnet=172.20.0.0/16 fortinet

# Start the docker container with the needed capabilities and a static ip
docker run -it --rm \
  --cap-add NET_ADMIN
  --dev /dev/ppp \
  --net fortinet --ip 172.20.0.2 \
  -e VPNADDR=host:port \
  -e VPNUSER=me@domain \
  -e VPNPASS=secret \
  auchandirect/forticlient

# Add route for you remote subnet (ex. 10.201.0.0/16)
ip route add 10.201.0.0/16 via 172.20.0.2

# Access remote host from the subnet
ssh 10.201.8.1

UPDATE: 2017/06/10
Docker's microkernel still lacks ppp interface support, so you'll need to use a docker-machine VM.

# Create a docker-machine and configure shell to use it
docker-machine create fortinet --driver virtualbox
eval $(docker-machine env fortinet)

# Start the priviledged docker container on its host network
docker run -it --rm \
  --privileged --net host \
  -e VPNADDR=host:port \
  -e VPNUSER=me@domain \
  -e VPNPASS=secret \
  auchandirect/forticlient

# Add route for you remote subnet (ex. 10.201.0.0/16)
sudo route add -net 10.201.0.0/16 $(docker-machine ip fortinet)

# Access remote host from the subnet
ssh 10.201.8.1

# Find out the container IP
docker inspect --format '{{ .NetworkSettings.IPAddress }}' <container>