This happens sporadically and I have not been able to come up with a (somewhat) reliable reproducer: Sometimes when creating an instance, it would get two private IP addresses assigned. 'nova interface-list <server>' would then list two interfaces instead of just one.

The problem is a bit annoying because assigning a floating IP address via 'nova floating-ip-associate' will bind it to the first address, though the instance actually uses the second address.

I have seen this issue with Mitaka as well as OSP9. In both cases I uses packstack to install a two host setup in which both hosts act as compute node and one of them in addition serves as network/controller node.

I have written a script which calls packstack and automatically creates four instances and seen the issue for two out of the four created ones. Interestingly, the faulty ones were started on different hypervisors so it does not seem to be related to where the instance comes up.

Is this behaviour known somehow? Not sure what additional info (apart from a reproducer) I could come up with to help track it down. Can you think of any forensic actions I could do on faulty instances in order to find out how this could have happened?