Problem with OpenStack Getting Started Guide

Daniel P. Berrange berrange at redhat.com
Tue Jan 3 18:35:28 UTC 2012


On Tue, Jan 03, 2012 at 11:29:40AM -0700, Steven Dake wrote:
> On 01/03/2012 05:32 AM, Mark McLoughlin wrote:
> > On Fri, 2011-12-23 at 13:16 -0700, Steven Dake wrote:
> >> Killing the first VM that was started (which has a MAC address equal to
> >> the br0) will cause deletion of vnet0 and cause the bridge driver to
> >> flush the arp table and choose a new bridge interface.  This results in
> >> disconnection of the remaining VM for 30-60 seconds.  
> > 
> > What exactly is happening during this time? The guest's routing table is
> > configured with the host as its gateway and it has a stale ARP cache
> > entry for the host?
> > 
> > Cheers,
> > Mark.
> > 
> 
> br0 adopts the mac address of the first interface added to it.  If the
> first interface added to it is removed, br0 finds a new mac address from
> the "next" interface in the bridge.  When the mac address is removed,
> the arp table is flushed for 30-60 seconds.

Aside from the connectivity blackout, this mac address also causes
pain for recent Windows guests, which will think they have been moved
to a new physical network everytime the MAC addr changes, causing them
to popup annoying dialog boxes on every login

Regards,
Daniel
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