[c-nsp] MTU on GigE

[Dave Temkin]

It worked for me.  I was doing AToM and IPSec tunneled over MPLS and was
able to push 2k+ MTU packets over it.  This wsa with pretty much the same
scenario of hardware/code you just described, also with 12.3T

-Dave

On Sun, 6 Nov 2005, Alex Rubenstein wrote:

>
>
>
> On Sun, 6 Nov 2005, Phillip Vandry wrote:
>
> > On Wed, Oct 19, 2005 at 02:54:47PM +0200, Vincent De Keyzer wrote:
> >> So you have a "physical" MTU, and a MTU for each protocol; and no "protocol"
> >> MTU can be higher than the "physical" MTU.
> >
> > Exception: "mpls mtu" (or "tag-switching mtu") can be larger than the
> > physical interface MTU... for some reason.
>
> Question is -- does it work?
>
> For instance, say you have a 7206, NPE-400, running 12.0S. It has a IO-FE.
> So, int f0/0 can only have a 'mtu' of 1500, but you can set the
> 'tag-switching mtu' to something much higher (say 9000).
>
> Suppose further, that you are doing some AToM on this 7206, and the
> interface you are AToM'ing is a DS3, with a MTU of 4470.
>
> Will it work? My limited memory remembers that this did work in one
> instance, but I can't say for sure.
>
> I thought the MTU issue on the FE cards of cisco was a physical one -- if
> so, why does this work? What is the real reason cisco fe cards can't do
> jumbo? non-technical?
>
>
>