[Openstack] ARP packets not sent during migration
On 03/23/2018 07:05 AM, Ramon Orru wrote:
> Hi Brian,
> yes, you're right, that's the point, libvirt is sending gARPs too
> early.... am I misconfiguring something? Seems to me a really strange
Sorry, don't know much about the libvirt side of things, maybe someone
more familiar with the Nova side of the migration would know?
> Il 21/03/18 22:35, Brian Haley ha scritto:
>> On 03/20/2018 12:40 PM, Ramon Orru wrote:
>>> 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
>>> 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.
>> Just to clarify - are you talking about connectivity to the floating
>> IP or just on the VLAN itself, i.e. the instance is directly connected
>> to the VLAN.Â I'm thinking it's the latter, which would mean it's
>> libvirt(?) sending the gARPs before the bridge is up?