Comment 11 for bug 1607412

The root cause of this problem is that the l3_router_plugin is incorrectly loading the DNS integration extension in the stable Mitaka branch. This extension should only be configured by the operator / deployer by adding 'dns' to the 'extension_driver' list in ml2_conf.ini. This bug was fixed for master (https://bugs.launchpad.net/neutron/+bug/1574694, https://review.openstack.org/#/c/311640) but not back ported to stable Mitaka.

This explains why when the compute manager queries Neutron for the enabled extensions the first two occasions (see my previous comment), it gets 'DNS Integration' in the list. The 'old' Neutron server (stable Mitaka) responded to these two queries:

http://logs.openstack.org/62/324262/3/gate/gate-grenade-dsvm-neutron-multinode/9af98c8/logs/old/screen-q-svc.txt.gz#_2016-07-25_10_04_25_207

http://logs.openstack.org/62/324262/3/gate/gate-grenade-dsvm-neutron-multinode/9af98c8/logs/old/screen-q-svc.txt.gz#_2016-07-25_10_15_04_868

The third occasion the compute manager queries for the enabled extensions, the response comes from the 'new' (Master branch) Neutron, where 'DNS integration' is not enabled:

http://logs.openstack.org/62/324262/3/gate/gate-grenade-dsvm-neutron-multinode/9af98c8/logs/new/screen-q-svc.txt.gz#_2016-07-25_10_25_13_702

Note that the failed port creation occurred right before the last extensions update:

http://logs.openstack.org/62/324262/3/gate/gate-grenade-dsvm-neutron-multinode/9af98c8/logs/new/screen-q-svc.txt.gz#_2016-07-25_10_24_49_250

The fix for this bug is to back port https://review.openstack.org/#/c/311640 to stable Mitaka