[ovirt-users] Ovirt causing strange network issues?

[Colin Coe]

Hi

We saw something very similar to this a couple of years ago.  In our case,
it was caused by STP being enabled on our hypervisors.

HTH



On 3 Oct. 2017 04:56, "Derek Atkins" <derek at ihtfp.com> wrote:

> 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 <(617)%20623-3745>
>        derek at ihtfp.com             www.ihtfp.com
>        Computer and Internet Security Consultant
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