[openstack-dev] [Neutron] HELP CONFIRM OR DISCUSS:create a port when network contain ipv4 subnets and ipv6 subnets, allocate ipv6 address to the port.

Neil Jerram Neil.Jerram at metaswitch.com
Mon Jul 20 12:01:32 UTC 2015

I am not completely sure, but I believe that the primary associations 
are that:

- a port is attached to a particular network

- a network may have an IPv4 subnet and/or an IPv6 subnet

- therefore, when a port is created, it gets an IPv4 address, and/or an 
IPv6 address, according to the subnets that are associated with the network.

Then the question is: what difference does it make if you add 
"--fixed-ip subnet_id=$[ipv4_subnet_id]" to your port creation command?

Unfortunately I don't know the answer to that.  However I do know that 
you can use "neutron port-update --fixed-ip ..." to _add_ an additional 
IP address to an existing port.  Therefore, and also considering your 
observations, I would guess that the effect of "--fixed_ip ..." is 
always strictly additional to the basic IP address allocation behaviour 
that you get based on the network and subnet associations.

Hope that may help...


On 20/07/15 04:26, zhaobo wrote:
> Hi ,
> Could anyone please check the bug below?
> https://bugs.launchpad.net/neutron/+bug/1467791
> This bug description:
> When the created network contains one ipv4 subnet and an ipv6 subnet 
> which turned on slaac or stateless.
> When I create a port use cmd like:
> neutron port-create --fixed-ip subnet_id=$[ipv4_subnet_id] 
> $[network_id/name]
> The specified fixed-ip is ipv4_subnet, but the returned port contained 
> the ipv6 subnet.
> If user just want a port with ipv4 , why returned port had allocated 
> an ipv6 address.
> And I know this is an design behavior from 
> http://specs.openstack.org/openstack/neutron-specs/specs/kilo/multiple-ipv6-prefixes.html#proposed-change
> But we are still confused about this operation.
> Thank you anyone could help for confirm this issue , and wish you 
> return the message asap.
> ZhaoBo
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