Normally with spanning tree, the switch goes into a wait mode before it
will pass traffic. This is to make sure that it isn't a switching loop. If
it ended up being a switch loop, it would cause a broadcast storm that took
down your entire network, and that's a Bad Thing(tm).

Portfast is a way of saying, "Hey, I know you're running spanning tree, but
this is REALLY NOT A SWITCH I PROMISE". The reason you'd do that is because
one of the first things that happens on a client machine as the TCP/IP
stack is brought up is a dhcp request is sent out. If that dhcp request is
sent while the port is still in blocking mode, then you don't get a lease
(or alternately, it takes forever to boot because the dhcp requests have to
timeout).

As you know, pxebooting is even earlier than the normal dhcp request, so
unless portfast is configured, you'll definitely be blocking when the PXE
request is sent.

Here's more info:
http://www.symantec.com/business/support/index?page=content&id=HOWTO6019(ignore
every instance of the word "Altiris")

--Matt


On Mon, Jan 14, 2013 at 2:36 PM, Morse, Richard E.MGH
<[email protected]>wrote:

> just introduced, sadly. But at least everything seems to be working so far.
>




-- 
LITTLE GIRL: But which cookie will you eat FIRST?
COOKIE MONSTER: Me think you have misconception of cookie-eating process.
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