[nsp] Virtual templates for ISDN users

[Scott]

> > interface Virtual-Template x
> >  mtu 1501
> >  ip mtu 1500
>
>
> :-)
>
> thanks, ive made a note in our kbase about that ...
>
> disabled it and setting global mtu worked for me ...
>
>
> while we on that subject ... could somebody explain the difference to me
> when it comes to those two commands ... should/should not be enabled...

well I'm no expert on it, but it's a bug in several IOS's.  The default is
1500 so you can't set "ip mtu 1500".  BUT if you set mtu 1501, then override
it with "ip mtu 1500" then the 1500 will stick and show in sh run.  It's a
workaround I came up more or less accidentally and with a Cisco technical
friend's help.  It's now part of a documented workaround in one of (or the
main) related bug.

Here'a a quote from with some of the technical explanations I had on file:
"mtu" is supposed to be the underlying layer 2 (interface) MTU
(net of layer 2 headers.)  "ip mtu" is the layer 3 MTU.  "ip mtu"
can't be larger than "mtu" but it can be smaller.
In looking at CSCdt91142 (which is the problem were a vaccess
can get a too-small MTU value), it seems that "ip mtu 1500" is
the reliable workaround (we hope).

HTH,
Scott