Re: Increase mtu? How?

Stuart Henderson <[email protected]>
Newsgroups gmane.os.openbsd.misc
Message-ID <[email protected]>
On 2026-06-05, Thomas Pries <[email protected]> wrote:
> Hi,
>
> Am 05.06.26 um 00:09 schrieb David Gwynne:
>> On Thu, Jun 04, 2026 at 10:52:10AM +0200, Thomas Pries wrote:
>>> ...
>>> ifconfig ix0/ix1?? hwfeatures ...??hardmtu 9198
>>> ifconfig aggr0?? hwfeatures ...??hardmtu 9198
>>> ...
>> OpenBSD is different to most other systems in how it handles packet
>> sizes and MTU on interfaces. ...
>
> Thank you very much for this detailed explanation.
>
> My network college would be happy, if I could would set the MTU to 9180 
> and I tried to set this on aggr0 and ix* via:
>
> ifconfig ix0 down
>
> ifconfig ix0 mtu 9180
>
> but I always get the error:
>
> ifconfig: SIOCSIFMTU: Device busy
>
> What is the procedure to set the MTU?

Set it before attaching the child interface. iirc once you've attached
to aggr/trunk you may need to detach before you can change it on the parent.
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