[openstack-dev] [nova] Multiple interfaces, same network

Ian Wells ijw.ubuntu at cack.org.uk
Mon Jul 22 19:20:38 UTC 2013

A while back (just before the summit, as I recall), there was a patch
submitted to remove the constraints on being able to connect multiple
interfaces of the same VM to the same Neutron network. [1]

It was unclear at the time whether this is a bug being fixed or a
feature being added, which rather stalled the discussion, along with
several 'eww, why would you do this' comments.  To that end, I've
added a blueprint to make the feature request [2], and I'd like to
bring the discussion here as to whether it's productive to do.

Personally, I want it because I want to simulate physical networks -
where it's perfectly legitimate to connect one machine to the same
network twice.  I can't simulate those networks without this feature.
I would argue that this makes people's lives easier in certain awkward
situations - if they have a VM configured to use two ports they can
use both ports on the same network if they wish - and is a low risk
change which should just work (something we can prove out with
adequate tests).  It also only affects anyone who actually tries to
connect one VM to the same network twice - that is, making the change
has no effect on the configurations that work today.

[1] https://review.openstack.org/#/c/26370
[2] https://blueprints.launchpad.net/nova/+spec/two-vifs-one-net

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