[j-nsp] weird MTU size on "show interface"

[Michel de Nostredame]

On Fri, Oct 1, 2010 at 4:10 AM, Wojciech Owczarek
<wojciech at owczarek.co.uk> wrote:
> This is just the way Juniper do things, just that it's not consistent
> across all of their platforms. I've once been told by a Juniper
> engineer that  1514 vs. 1518 MTU value is  displayed (on the EX
> platform at least) because the 4 bytes of CRC are not taken into
> account as the CRC is not part of the media MTU (which kind of makes
> sense). Excerpt from "Configure the Media MTU" in Juniper docs:
>
> "The actual frames transmitted also contain cyclic redundancy check
> (CRC) bits, which are not part of the media MTU. For example, the
> media MTU for a gigabit Ethernet interface is specified as 1500 bytes,
> but the largest possible frame size is actually 1504 bytes; you need
> to consider the extra bits in calculations of MTUs for
> interoperability."
>
> So while not really a problem, this does cause some confusion.
>
> HTH,
>
> Cheers,
> Wojciech

Thanks Felix and Wojciech,

As you mentioned that is display problem and causes some confusion. I
checked other Cisco Catalyst switches and I found similar "display"
problem (or feature :p ). The switch interfaces no matter access or
trunk are displayed with MTU 1500.

I assume that is common display behavior on the switch interface in
both Cisco and Juniper.

Regards,
--
Michel~