[ovirt-users] Ovirt causing strange network issues?

[Derek Atkins]

Hi,

I'm at my wits end so I'm tossing this here in the hopes that SOMEONE
will be able to help me.

tl;dr: Ovirt is doing something on my network that is causing my fiber
modem to go from 3-5ms to 300-1000+ms round trip times.  I know it's
ovirt because when I unplug ovirt from my network the issue goes away;
when I plug it back in, the issue recurs.

Long version:

I've been running Ovirt 4.0.6 happily on CentOS 7.3 for several months
on a single host machine. Indeed, the host had an uptime of 200+ days
and was working great until approximately midnight, September 21/22
(just over a week ago).  I was on an airplane halfway across the
Atlantic at that time, so it wasn't anything I did.

My network is configured as:

  fiber modem <-> edgerouter <-> switch <-> everything else

ovirt is living in the "everything else" area.

When I sit with a laptop connected to either the everything else range
or even directly connected to the fiber modem, I run 'mtr' and see
network times (starting at the fiber modem) that bounce all over the
place.  When I unplug ovirt I see consistent 3-5ms times.  Plug it back
in, voom, back up to badness.

I've spent several hours plugging and unplugging different devices
trying to isolate the issue.  The only "device" that has any effect is
my ovirt box.

I have tried to debug this in several ways, but really the only thing
that seems to have helped at all is shutting down all the VMs and the
hosted engine.  Once nothing else is running (but the host itself), only
then does the network seem to return to normal.

I'm really at my wits end on this; I have no idea what is causing this
or what might have changed to cause the issue right at that time.  I
also can't imagine what ovirt is doing over the network that could cause
the modem, two physical hops away, to lose its mind in this way.  But my
experiementation is definitely showing a direct correlation.

Help!!

-derek

-- 
       Derek Atkins                 617-623-3745
       derek at ihtfp.com             www.ihtfp.com
       Computer and Internet Security Consultant