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[Openstack] ARP packets not sent during migration


Hello everybody, I'm running a fresh queens cluster. I'm using bridges 
to support networking. I'm facing an issue when an instance is live 
migrated.
Suppose we have an instance running with an interface on vlan XXX, and 
we want to migrate it to compute host YYY. We'll call that instance ZZZ.
If no other instance is already running on YYY using vlan XXX, no bridge 
called 'br-vlan.XXX at br-vlan' exists yet on YYY.
Now, if I migrate ZZZ on YYY host, a new bridge 'br-vlan.XXX at br-vlan' 
will be created.
During the migration process, ZZZ become unreachable while interfaces 
are going up on YYY (from 10 seconds to about 2 minutes).
After some troubleshooting, we spotted the problem: bridge 
'br-vlan.XXX at br-vlan' is being created after gratuitous ARP packets are 
sent from migrating machines to advise other devices about new position.
The result is: no other device can reach the fresh migrated machine 
until ARP table becomes stale.
This does not happen when an instance with an interface on same vlan is 
already runnning on destination host ('br-vlan.XXX at br-vlan' is already 
up and running, and ARPs can be sent flawlessly).

Any idea of how to get rid of this? I think it's very unlikely that I'm 
the first to face this problem, but i didn't manage to find additional 
info on this strange behaviour.
Thanks in advance.

Ramon