Creating VM directly on external network.

Hi I have a charm based OpenStack setup. The network topology is as below. Creating vms on the internal network and adding floating ips works as expected. Adding vms on directly on to the ext_net does not. openstack allows me to do it, but I get host is unreachable when trying to connect. Is there some configuration I have missed? Thanks [cid:3699cab3-ea6a-45eb-91c3-65e91056fd71]