> From: [email protected] [mailto:discuss-
> [email protected]] On Behalf Of Morse, Richard E.MGH
> 
> Hi! Thanks to everyone who responded with suggestions! Apparently, it
> works if I turn *off* spanning-tree on the child switch, leaving the parent
> switch configured with RSTP. I'm not sure why, not what deleterious side
> effects I've just introduced, sadly. But at least everything seems to be
> working so far.
> 
> Is "portfast" the same thing as "edge port"? If so, I may go over again and
> look more closely at those settings.

Just to make sure you know what to be afraid of, definitely DON'T do this with 
STP disabled:

Take an ethernet cable.  Click both ends into the same switch.  If you do this, 
you will almost instantaneously bring down the whole network, while all forms 
of traffic are propagated endlessly in a circle.  

This error is kind-of rare (but certainly not unheard of) as long as you have 
just one switch in the closet, with fairly untangled cables.  But this problem 
becomes much more common when you have network closets connected to network 
closets, and people scatter little 5-port switches throughout the office, and 
then "bring your child to work day" comes around, and one of the negligent 
parents allows their kid to play with an ethernet cable.

With spanning tree protocol enabled, the switch waits 30 seconds before 
allowing any traffic to pass.  It's detecting loops and disables that port if a 
loop is detected.  When you disable stp, you're saying, "don't do that annoying 
30 second wait thing.  I accept the risk.  I want the ethernet to come on 
immediately when a cable is connected."

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