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Why would DHCP intermittently assign 2 IP addresses?

asked 2016-06-16 03:19:06 -0500

mickt gravatar image

I have a mitaka installation running in docker containers; dockerisation should be irrelevant. I notice that the DHCP server intermittently assigns 2 IP addresses to instances. Anyone know why this might be? I also currently have HA enabled and this too should be irrelevant as I see the same behaviour with HA disabled.

I boot instances as follows:

nova boot --flavor m1.tiny --image cirros --nic net-id=f6a73223-5dbe-4bc6-94e6-aaca898a844d --security-group default --key-name cloud test

nova list:


| ID | Name | Status | Task State | Power State | Networks |


| b4aee59e-c08b-49d2-8ae9-33e9b6708a49 | test | ACTIVE | - | Running | int-net=, |

| 4c697b2f-41d3-4456-b994-4d311f2d7785 | test1 | ACTIVE | - | Running | int-net=, |

| 75f34b58-3b38-4c19-b922-fff1a0e84002 | test2 | BUILD | spawning | NOSTATE | int-net= |



You can see that instance test1 has two IP addresses assigned from

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On further test I notice that scheduling shows 1 IP & spawning shows 2:

e237380e-6812-40c7-98f0-06b629b9d709 | test1 | BUILD | scheduling | NOSTATE | int-net=

e237380e-6812-40c7-98f0-06b629b9d709 | test1 | BUILD | spawning | NOSTATE | int-net=,

mickt gravatar imagemickt ( 2016-06-16 09:19:26 -0500 )edit

We hit the same behavior after 2nd bridge was added to following config: /etc/neutron/plugins/ml2/openvswitch_agent.ini - bridge_mappings. when you specify --availability-zone nova:compute1 (AZ with only 1 node) the problem is gone - instance has only 1 expected IP.

jan-kaufman-w gravatar imagejan-kaufman-w ( 2016-06-20 09:35:08 -0500 )edit

We are also Facing same problem using Mitaka on Ubuntu with ODL plugin.

bsrgsit gravatar imagebsrgsit ( 2016-06-22 23:54:04 -0500 )edit

Alas, AZ do not resolve my issue.

mickt gravatar imagemickt ( 2016-07-14 09:28:54 -0500 )edit

We have the same issue on Mitaka with opensuse_Leap_42.1 and don't know how to fix it yet.

eblock gravatar imageeblock ( 2016-07-28 05:38:41 -0500 )edit

5 answers

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answered 2016-06-20 09:27:32 -0500

Arteal gravatar image

Same happens to us, from time when we added second bridge mapping to :


And it happens only when you do not specify availability zone to specific node.

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Sending availability zone solved problem for me too.

shital gravatar imageshital ( 2017-03-16 08:33:15 -0500 )edit

answered 2016-06-20 08:57:37 -0500

Hi Mickt,

we are experiencing the same thing on Ubuntu 14.04 w/ Cloud archive Mitaka. Have you solved the issue already?

Regs David

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Not yet, it is low priority for me at moment but is on my to-do list.

mickt gravatar imagemickt ( 2016-07-29 02:29:48 -0500 )edit

answered 2017-06-02 04:00:00 -0500

zhangoic gravatar image

updated 2017-06-02 04:06:52 -0500

I hit this problem either. I don' think it has any relation with bridge-mapping. In my experice, I found that vm spawn has two scheduling process. In the first one, the tap interface in ovs has been created by nova-compute, and the port status in neutron db was active. But then, the compute node met qemu error (CPU feature were not found). The exception made nova-scheduler to reschedule. The second process would also create port and ovs interface by a new compute node. As a result, it has two port in neutron. After I closed the fault one, the problem was dissappeared. All new created vm had only one port.

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answered 2020-03-25 04:49:13 -0500

John Dw. gravatar image

This happens in mitaka when in one cluster started two or more nova-scheduler's

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answered 2017-09-05 05:02:47 -0500

Hello zhangoic,

Can you help me to fix same issue? Or can you tell me what changes was made to solve it?


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Asked: 2016-06-16 03:19:06 -0500

Seen: 1,525 times

Last updated: Jun 02 '17