[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
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.