External networks are used to attach Neutron routers to the physical network and help provide routing in and out of a project via routes and floating IPs. When a network's external attribute is set to True, the network is shared among all projects. Access policies can be used to limit external networks to a subset of projects. The syntax for creating a policy for external networks is very similar to the policy demonstrated in the last section. The action, however, will change from access_as_shared to access_as_external.
In this example, an external network named MySemiSharedExternalNetwork using VLAN 31 has been created with the goal of sharing it with a subset of projects. Notice that the shared attribute is False and that the external attribute is internal, meaning that it can only be used for internal networks:
As a result, the...
