[c-nsp] setting max mtu on switch (Jumbo)

[Mark Tinka]

On Tuesday, May 29, 2012 10:40:38 AM Reuben Farrelly wrote:

> I've often wondered about supposed downsides myself.  Why
> is it that we don't see the layer 2 MTU set as high as
> possible on Cisco devices out of the box, but a
> relatively "normal" routing MTU set to 1500 in the
> default config?   Are there any "bad things" that could
> come out of this config?
> 
> Some of the HP (Flex 10 etc) switches we run here do
> jumbos by default and I don't think there is any way to
> lower it. Then again these are storage switches so....

It's probably because the only standards-based MTU value is 
1,500 bytes, and the value for Jumbo frames has been 
recognized as a standard.

As such, while all major vendors will support even up to 
10,000 bytes in some cases, 1,500 bytes is still the 802.3 
understood standard.

You can read here about how the industry is trying to adopt 
Jumbo frames as some kind of "common understanding":

http://en.wikipedia.org/wiki/Jumbo_frame#Adoption

Mark.