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xen-users
Re: [Xen-users] Automatically broadcast arp during a live migration.
On 1/28/07, Ralf Schenk <rs@xxxxxxxxxx> wrote:
Michael Marineau schrieb:
> I am using Xen 3.0.4 on Gentoo. During a vm migration there is not an
> automatic arp broadcast to notify the switch the vm has changed
> network ports. This is not an issue if the vm is sending traffic at
> the time or another system sends an arp broadcast requesting the
> address for the vm. Both of which will cause the switch to update
> which port the vm is on. However if neither of those things happen all
> traffic to the vm will stall.
>
> An easy way to demonstrate this is to start arping (from somewhere
> other than the destination dom0) before the migration, ie:
> arping <vm ip address>
> As soon as the migration finishes pings will stop.
>
> An easy workaround is to do the same thing, but broadcast all pings so
> the switches arp cache doesn't prevent the delivery of the ping.
> arping -b <vm ip address>
>
> So my questions are:
> Is Xend supposed to handle this issue automatically but for some reason
> is not?
> And if it isn't supposed to is there a good place to hook this into
> Xend so it does handle it?
Hello !
I'm testing xen live migration, too. I use drbd 8.0
(http://www.drbd.org) in primary/primary mode with OCFS2 on top.
I want to confirm your observations. Did you get any hint what can be
done to make the switches learn the new situation faster ?
Of course it would be sufficinet to let a deamon ping an external (=not
in the cluster) host in fast intervals but I would also like XEND to
handle this as it knows about the mac adress and the right time to send
out the broadcast arp.
I plan on writing a script to hook into xend via it's
external-migration-tool setting to broadcast the arp ping when the vif
device finishes moving, but I have not gotten around to it yet. I will
give that method a try later this week probably.
--
Michael Marineau
Oregon State University
mike@xxxxxxxxxxxx
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