From: Jay Hennigan (jay@xxxxxxxx)
Date: Wed Aug 28 2002 - 12:32:20 GMT-3
On Wed, 28 Aug 2002, Colin Barber wrote:
> Yes it does. The only thing that portfast does is make a port go straight
> into forwarding mode on becoming active. It still sends/receives BPDUs and
> will block the port if it detects a loop. If the loop is then removed the
> port will go through listening and learning states.
Contrast this with spantree-disable which is a similar command used in
IOS-based layer 3 switches such as the 2948G-L3, or on routers where
multiple ethernet ports are part of a bridge group.
See:
http://www.cisco.com/warp/public/473/12.html
spantree-disable is more dangerous than portfast if other than a leaf
node is connected to the port(s) as this command WILL ignore BPDUs.
BTW, another advantage to portfast is that it supresses TCNs which will
avoid the fast-flush of the MAC address tables on the network associated
with a port moving to forwarding.
-- Jay Hennigan - CCIE #7880 - Network Administration - jay@west.net NetLojix Communications, Inc. - http://www.netlojix.com/ WestNet: Connecting you to the planet. 805 884-6323
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