[ovirt-users] Logical Networks with different MTUs

[Yevgeny Zaspitsky]

Hello Cam,

The problem you described seems to be similar to the described in
https://bugzilla.redhat.com/show_bug.cgi?id=1242227.
The mentioned bug was fixed in one of the recent oVirt builds.
The updated Ovirt code allows to mix networks (regardless of them being VM
or non-VM) on a single NIC with the following conditions:

   - not more than one non-VLAN network in conjunction with any number of
   VLANs
   - MTU of the VLAN networks have to be equal to that of a non-VLAN one if
   such exists

So I'd advise you to update you oVirt to the latest build.

Regards,
Yevgeny

On Tue, Oct 6, 2015 at 2:47 AM, Cam Wright <cwright at cuttingedge.com.au>
wrote:

> Hi,
>
> I've just started building an oVirt farm as a replacement for our
> existing infrastructure and I'm having issues configuring multiple
> VLAN bridges with different MTUs.
>
> When I try to add a logical network with a VLAN tag + VM Network + MTU
> 9000 to a bonded interface on my host with only the ovirtmgmt network
> (MTU 1500, default) it throws up an error message and won't let me
> continue, error message below:
>
> Cannot setup Networks. The following Logical Networks do not have the
> same MTU value: ovirtmgmt(default),
> net_bne_vlan10(9000).
>
> Eventually, I will want to add more logical networks with the default
> MTU, so setting the ovirtmgmt MTU to 9000 is unfortunately not going
> to solve my issue.
>
> This is something I can do in vanilla Linux networking where I set the
> 802.3ad bond to be MTU 9000 and configure two different bridges off
> that interface to 1500 and 9000, however this does not seem to be
> possible in the oVirt web interface.
>
> I've dug through the Administration guide and feature requests and
> there doesn't seem to be anything there around using different MTU
> values for different logical networks.
>
> Has anyone been able to successfully do this? The
> /etc/sysconfig/network-scripts and /var/lib/vdsm/persistence/netconf
> files seem to get rewritten whenever the vdsm service does anything,
> so I'm reluctant to edit them manually.
>
> The hosts were built using the hosted-engine installer on Fedora 22.
> The engine is running Fedora 22 also, see below:
>
> [root at bne-ovirtengine01 ~]# cat /etc/redhat-release
> Fedora release 22 (Twenty Two)
> [root at bne-ovirtengine01 ~]# uname -r
> 4.0.4-301.fc22.x86_64
>
> oVirt Engine Version: 3.6.0-1.fc22
>
> Any assistance would be appreciated.
>
> Cam Wright | Systems Administrator
> CUTTINGEDGE
> 90 Victoria St, West End, Brisbane, QLD, 4101
> T +61 7 3013 6222
> E cwright at cuttingedge.com.au | W www.cuttingedge.com.au
>
> /SYD /BNE /MEL /TYO
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