[c-nsp] UDLD vs Auto-neg

[Afsheen Bigdeli]

 From the documentation:

"At Layer 1, autonegotiation takes care of physical signaling and fault 
detection. UDLD performs tasks that autonegotiation cannot perform, such 
as detecting the identities of neighbors and shutting down misconnected 
interfaces. When you enable both autonegotiation and UDLD, the Layer 1 
and Layer 2 detections work together to prevent physical and logical 
unidirectional connections and the malfunctioning of other protocols."

See the 'Configuring UDLD' section of any recent software config guide 
for more info.

--afsheenb

Tim Durack wrote:
> A question that's been bugging me for a while: what does UDLD give me
> that running auto-neg on both sides of a link doesn't? If I run auto,
> link drops if the pathway goes one-way, and won't renegotiate until
> the pathway is re-established. Isn't that all UDLD does?
> 
> Perhaps there are some failure modes I'm not considering. Or maybe it
> has more to do with not running auto on infrastructure links.
> 
> Comments would be appreciated!
> 
> Tim:>
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