If the external VN is created through UI and network deleted through neutron, then see following error (there are not ports in the VN):


root@nodeg10:~# neutron net-delete pub-test
Unable to complete operation on network 6b8421b2-197c-43ed-9f5a-4e2e7765baa0. There are one or more ports still in use on the network.

root@nodeg10:~# neutron net-show pub-net
Unable to find network with name 'pub-net'
root@nodeg10:~# neutron net-show pub-test
+-------------------------+---------------------------------------------------------------------------------------------------------------+
| Field                   | Value                                                                                                         |
+-------------------------+---------------------------------------------------------------------------------------------------------------+
| admin_state_up          | True                                                                                                          |
| contrail:fq_name        | default-domain                                                                                                |
|                         | demo                                                                                                          |
|                         | pub-test                                                                                                      |
| contrail:instance_count | 0                                                                                                             |
| contrail:subnet_ipam    | {"subnet_cidr": "17.8.9.0/24", "ipam_fq_name": ["default-domain", "default-project", "default-network-ipam"]} |
| id                      | 6b8421b2-197c-43ed-9f5a-4e2e7765baa0                                                                          |
| name                    | pub-test                                                                                                      |
| router:external         | True                                                                                                          |
| shared                  | False                                                                                                         |
| status                  | ACTIVE                                                                                                        |
| subnets                 | 7a3aeb69-8e0a-4eab-983e-c2285d296927                                                                          |
| tenant_id               | 2fa9fa7be540434290dcb81433981b77                                                                              |
+-------------------------+---------------------------------------------------------------------------------------------------------------+

NoIdError: Unknown id: Error: oper 2 url /virtual-machine-interface/e32fda94-b604-4ba5-b081-e0089c28fb36 body {'fields': 'instance_ip_back_refs'} response No virtual-machine-interface object found for id e32fda94-b604-4ba5-b081-e0089c28fb36
2014-06-18 22:43:55.987    ERROR [neutron.api.v2.resource] delete failed
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/neutron/api/v2/resource.py", line 84, in resource
    result = method(request=request, **args)
  File "/usr/lib/python2.7/dist-packages/neutron/api/v2/base.py", line 432, in delete
    obj_deleter(request.context, id, **kwargs)
  File "/usr/lib/python2.7/dist-packages/neutron_plugin_contrail/plugins/opencontrail/contrailplugin.py", line 314, in delete_network
    raise e
NetworkInUse: Unable to complete operation on network 6b8421b2-197c-43ed-9f5a-4e2e7765baa0. There are one or more ports still in use on the network.