ifconfig em0 mtu 9000 does not update the routing table

[Nikolay Denev]

On 28 Oct, 2008, at 18:41 , Jack Vogel wrote:

> It can't change the route table when you've given it no address:
>
> IE. ifconfig em0 HOSTNAME mtu 9000 will update it just fine.
>
> Cheers,
>
> Jack
>
>
> On Tue, Oct 28, 2008 at 6:15 AM, Nikolay Denev <ndenev at gmail.com>  
> wrote:
> Hello,
>
> As the subject says, I'm trying to enable jumbo frames on running  
> machine by setting
> ifconfig em0 mtu 9000 by hand, but nothing changed, and I've fount  
> that when I list
> the routing table with the MTU column it shows the connected routes  
> still with MTU 1500.
> Is this supposed to work this way? I understand that making ifconfig  
> touch the routing table is ugly hack, but maybe the routing code can  
> be notified for interface changes by some other mechanism?
>
> btw, this is on 7-STABLE with if_em(4) interfaces.
>
> --
> Regards,
> Nikolay Denev
>


Hi Jack,

Yes, I understand that, It just looked logical to me to update the  
existing entries (directly attached) if no address is given, so one  
can use the mtu knob alone.

Anyways, one rarely touches the mtu alone and this not a real problem,
  I've just tried to enable jumbo frames on two running machines with
just the ifconfig em0 mtu 9000 line and wondered why it does not work  
for a minute.

Thanks!

--
Regards,
Nikolay Denev