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@br-vlan' exists yet on YYY.
Now, if I migrate ZZZ on YYY host, a new bridge 'br-vlan.XXX@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@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@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. I'm thinking it's the latter, which would mean it's
libvirt(?) sending the gARPs before the bridge is up?
-Brian
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