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How does neutron choose subnet [closed]

asked 2017-04-26 07:22:28 -0500

pquigs gravatar image

I have Mitaka installed, running classic Open vSwitch implementation with core components plus Horizon and Heat. I have a private network defined with 2 subnets. I've read that you cannot control which subnet an instance is deployed to, though it would be a nice "feature" to add ;-)

My question is this - how does neutron choose a subnet? In my case, it seems to pick the most recent one that I defined, but I'm guessing that's just due to the names. Is there an algorithm that explains the subnet selection process?


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Closed for the following reason the question is answered, right answer was accepted by pquigs
close date 2017-10-13 11:46:34.174690

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answered 2017-05-07 11:59:25 -0500

mlschuler gravatar image

updated 2017-05-16 14:34:37 -0500

If you have defined several subnets in a single network you may choose the subnet a port is created in. The syntax is: openstack port create --network <network> --fixed-ip subnet=<subnet> <port-name>. If you do not choose a subnet, I do not know what subnet Neutron chooses. (Newton release)

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Of course! I guess my question really was to see if I could influence which subnet was used to deploy the instance. I did find references to: openstack sever create ... --nic net-id=net-uuid,subnet-id=nnnnnnn... BUT, that doesn't seem to work.

pquigs gravatar imagepquigs ( 2017-05-08 13:05:16 -0500 )edit

Bottom line - I am trying to specify which subnet to use when deploying a VM. I have 1 net with 2 subnets. Would like to say "deploy to subnet2" for example. I found some discussion of a subnet-id parm under net-id on the openstack server create, but that doesn't seem to be implemented.

pquigs gravatar imagepquigs ( 2017-05-09 14:01:12 -0500 )edit

OK, suppose the better approach is 1 subnet with multiple pools. THX!

pquigs gravatar imagepquigs ( 2017-05-09 14:02:13 -0500 )edit

You create a port as mschuler shows above, then launch the instance using openstack server create --nic port-id=....

Bernd Bausch gravatar imageBernd Bausch ( 2017-05-16 14:52:22 -0500 )edit

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Asked: 2017-04-26 07:22:28 -0500

Seen: 205 times

Last updated: May 16 '17