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From: Craig Boston <craig@feniz.gank.org>
To: Brooks Davis <brooks@one-eyed-alien.net>
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Subject: Re: em device hangs on ifconfig alias ...
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On Mon, Jul 10, 2006 at 02:56:27PM -0700, Brooks Davis wrote:
> On Mon, Jul 10, 2006 at 05:55:23PM -0300, User Freebsd wrote:
> > >On Mon, Jul 10, 2006 at 12:11:36AM -0400, Mike Tancsa wrote:
> > >Of course, any reasonable administrator would configure
> > >
> > >	interface FastEthernet0/1
> > >	 spanning-tree portfast

> It tells the switch that this port will never be anything but a leaf in
> the tree so STP does not need to re run before allowing packets to flow.
> If you do this and then create a loop with it, bad things happen, but
> cisco recommends it in general.

Note that STP still runs, it just doesn't start out blocking the port.
Any "bad things" will only happen until the switch figures out that
there is a loop, which usually happens fairly quickly.

Worst case scenario: you may have a packet storm for a second or two.
All the switches I've tried it on detect the loop very quickly (after
only a few packets), so I usually just enable portfast across the board.

Craig