openstack network create --external --provider-physical-network physnet1 --provider-network-type flat public1

openstack subnet create --no-dhcp --allocation-pool start=192.168.1.100,end=192.168.1.200  --network public1 --subnet-range NETWORK/CIDR  --gateway 192.168.1.1 public1-subnet

openstack network create --provider-network-type vxlan demo-net
openstack subnet create --subnet-range 192.168.1.0/24 --network demo-net \
    --gateway 10.0.0.1 --dns-nameserver 8.8.8.8 demo-subnet

openstack router create demo-router
openstack router add subnet demo-router demo-subnet
openstack router set --external-gateway public1 demo-router