When attaching a Neutron router an external network, the respective network must have its router:external attribute set to True to be eligible for use as an external network. Otherwise, the command will fail. The GATEWAY_NET network created previously meets this requirement.

Using the openstack router set command, attach the router MyLegacyRouter to the GATEWAY_NET network:

openstack router set --external-gateway GATEWAY_NET MyLegacyRouter 

No output will be returned upon successful completion of the command. Using the openstack port list command, determine the external IP address of the router:

In this example, the IP address assigned to the router's external interface is 10.30.0.106.