[ale] Higher MTU for 40 GB NICs?

[Jim Kinney]

I totally disagree. Anything running on a 40 Gbit interface is not going to
hit a vpn or other mtu-eating process. Any vpn traffic would be a subset.

Find out what the device will support and max the mtu to that. When it
negotiates with the next device, it will adjust the mtu down as required.
If the switch is decent quality, all 40 Gbit will from my research, the mtu
down shift will not be for the entire unit but per port as required.

Setting an MTU below 1500 is really only to avoid fragmentation on long
haul line when running encryption or ppp to make up from crappy software.
On Jun 7, 2016 4:33 PM, "leam hall" <leamhall at gmail.com> wrote:

> I'm of the opposite opinion, having been bitten by downstream devices.
> I generally set it to 1460 or so if the interface sends anything
> outside of my control. Which is most things. If you're using an
> interface dedicated to backend storage, then the higher MTU can help
> some. No metrics for that, but that's my understanding.
>
>
>
> On Tue, Jun 7, 2016 at 3:29 PM, dev null zero two <dev.null.02 at gmail.com>
> wrote:
> > absolutely increase it, it lowers the overhead of TCP. 9000 should be the
> > default MTU for 10 GB links at a minimum. be wary of packet
> fragmentation if
> > they end up somewhere that isn't configured to use that MTU though.
> >
> > On Tue, Jun 7, 2016 at 3:22 PM, Lightner, Jeffrey <
> JLightner at dsservices.com>
> > wrote:
> >>
> >> Is there any intrinsic benefit to using a higher MTU for 40 GB NICs?
> >>
> >>
> >>
> >> That is, with all other things being equal is there any benefit to
> setting
> >> it higher on a 40 GB than on a 10 GB or 1 GB?
> >>
> >>
> >>
> >> I notice 40 GB defaulted to 1500 just like the 1 GB and 10 GB.
> >>
> >>
> >>
> >> The only time I’ve mucked with MTU in recent memory was because a vendor
> >> insisted it would solve a problem.   (It didn’t because the issue wasn’t
> >> networking in the first place but that is another story.)
>
>
> --
> Mind on a Mission
>
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