Portfast

Answered Question
Feb 5th, 2009
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Hi,


If i enable Portfast in the switch, does STP still works in that port.


By chance if i connect a switch in that port, what will happen?


R.B.Kumar

Correct Answer by Roberto Salazar about 8 years 1 month ago

Yes, it does. The port just do not go through learning and immediately go to forwarding, but STP still runs on that port.

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Correct Answer
Roberto Salazar Thu, 02/05/2009 - 10:45
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Yes, it does. The port just do not go through learning and immediately go to forwarding, but STP still runs on that port.

Richard Burts Thu, 02/05/2009 - 10:47
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RB


If you configure portfast then STP does still run in that port. Portfast does not disable STP but only changes the behavior a little so that instead of going through the stages of listening and learning before going to forwarding with portfast the port goes immediately into the forwarding state. But it does still run STP.


If you connect a switch on that port it has the possibility that you could connect another port on the second switch to a port on the first switch and create a loop. If the loop is created and portfast is enabled there will be a great increase in traffic over those ports until STP is able to detect the loop and force one of the ports into blocking mode.


HTH


Rick

hclisschennai Thu, 02/05/2009 - 10:50
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Hi Rick,


Thanks, i got it. Thus for we have to enable portfast BPDU Guard to aleviate the interim flooding due to the time it takes to find the Loop using normal STP process

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