[libvirt-users] OVS / KVM / libvirt / MTU

[Peter Crowther]

On Thu, 8 Aug 2019 at 10:08, Sven Vogel <S.Vogel at ewerk.com> wrote:

> The question for me is why they use the smallest?
>

Because otherwise some frames won't get through because the interface can't
receive them, and the job of network equipment is to enable and maintain
communication :-).

>
> Cheers
>
> Sven
>

- Peter

[...]
>


> Am 31.07.2019 um 15:50 schrieb Alvin Starr <alvin at netvel.net>:
>
>
> In general if no MTU is set on interface creation the default value is
> 1500.
>
> On OVS the bridge MTU is automatically set to the smallest port MTU. So
> you just have to set the MTU of each port of the bridge.
>
> Take a look at: https://bugzilla.redhat.com/show_bug.cgi?id=1160897
> It is a bit of a pain to read but seems to confirm the statement about the
> OVS MTU value being set by the MTU of the ports.
>
> I have been using OVS with Xen and a few years ago I had to wrap my head
> around this problem.
> Once you start setting the MTU to something other than 1500 you will find
> you need to set ALL the MTU values of ALL your interfaces.
> Otherwise some inherited default will bite you.
>
>
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