FWIW, I actually like the 9k default as I suspect it means that the code path
for jumbo frames gets tested a lot more than is normal. If 1500 is the default
I suspect jumbo frame bugs will begin to creep in and go unnoticed.
It was nice not having to fix any 9k bugs when we started using VPP. :)
With that in mind, a local config default override seems better than a compiled
default change.
Thanks,
Chris.
> On Feb 26, 2020, at 10:07 AM, Dave Barach via Lists.Fd.Io
> <dbarach=cisco....@lists.fd.io> wrote:
>
> OK, how about this: I’ll add a VLIB_CONFIG_FUNCTION, or [more likely] add a
> system default MTU parameter to one of the existing config functions.
>
> I’m sick of cluttering configs with interface MTU commands...
>
> Thanks... Dave
>
> From: John Lo (loj) <l...@cisco.com>
> Sent: Wednesday, February 26, 2020 9:47 AM
> To: Dave Barach (dbarach) <dbar...@cisco.com>; vpp-dev <vpp-dev@lists.fd.io>
> Subject: RE: Change interface default MTU to 1500
>
> Hi Dave,
>
> My memory was that in data center or cloud environment it is desirable to set
> MTU to jumbo frame size to avoid fragmentation by default. Thus the question
> would be if it is reasonable to set default MTU size to 9000 for VPP and what
> kind of problem is it causing that would be fixed by changing it to 1500.
>
> Regards,
> John
>
> From: vpp-dev@lists.fd.io <vpp-dev@lists.fd.io> On Behalf Of Dave Barach via
> Lists.Fd.Io
> Sent: Wednesday, February 26, 2020 8:40 AM
> To: vpp-dev <vpp-dev@lists.fd.io>
> Cc: vpp-dev@lists.fd.io
> Subject: [vpp-dev] Change interface default MTU to 1500
>
> Folks,
>
> I’m considering changing the default interface MTU to 1500, from the current
> value of 9000:
>
> ethernet_register_interface (...)
> {
> <snip>
> /* Standard default ethernet MTU. */
> vnet_sw_interface_set_mtu (vnm, hi->sw_if_index, 9000);
> <snip>
> }
>
> I’ve pinged some folks, and nobody remembers why we’re setting the default
> MTU to 9000.
>
> Thanks... Dave
>
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