# This answer is based on the default microstack example from site below:
# https://ubuntu.com/openstack/install
# Type the below commands in the machine that hosts microstack
sudo iptables -t nat -A POSTROUTING -s 10.20.20.1/24 ! -d 10.20.20.1/24 -j MASQUERADE
sudo sysctl net.ipv4.ip_forward=1