[c-nsp] QOS Configuration Help

[Justin Shore]

Dan Letkeman wrote:
> On Wed, Mar 5, 2008 at 4:42 PM,  <A.L.M.Buxey at lboro.ac.uk> wrote:
>>  switchport nonegotiate  - so link cant become a trunk with malicious
>>  endpoint,  spanning-tree portfast,   (its not a trunk)

This is OT for this discussion but nonegotiate doesn't actually prevent 
a trunk from forming.  It's a common misconception, one that I used to 
suffer from myself.  The possible modes are:

Acccess - Forces non-trunking mode and will negotiate to set up 
non-trunking links (though I don't know of a case when this negotiation 
actually does something)

Dynamic Desirable - default for all LAN interfaces - makes the port use 
DTP to negotiate a trunk if possible but will fall back to access if 
needed.  To create a trunk the neighbor must be auto, desirable or trunk.

Dynamic Auto - Same as Desirable only the other side must be either a 
trunk of desirable port.

Trunk - Forces trunking and negotiates to set up trunks with Desirables 
and Autos.

No-negotiate - Forces trunking but will not negotiate anything.


So by setting ports to nonegotiate you're actually forcing the port into 
trunk mode.  The wording is a little weird unless the admin has a clear 
understanding of the 5 possible modes, even when most people only ever 
use 2 of them.

Justin