Re: Basic q regarding STP initial convergence

Hi Keegan

I think you're confusing the blocking state with blocked ports.
There is an initial blocking state, when a switch is 1st powered on, which
lasts 20 secs (as far as im aware).
This time cannot be modified.
During this time, a switch can only receive bpdus, it cannot transmit bpdus
or send/rx data.

I was referrring to the initial stp convergence.
You are referring to stp topology changes causing a blocked port to
transition to forwarding state.
The only blocking state occurs at initialisation..ports which are blocked
after convergence are not in the blocking state.

HTH,

Roy

There is a difference between the initial blocking state of 20 secs

2009/8/9 <Keegan.Holley_at_sungard.com>

> I think you're confusing the listening and blocking states. The blocking
> state is when it has already converged and knows to block a port. Listening
> is when it's trying to see if it's the root. For example if the STP
> algorithm decided a blocking port was going to transition to forwarding why
> would it block for an additional 20s before listening and not passing
> traffic for an additional forwarding-delay?
>
> HTH,
>
> Keegan
>
>
>
> *Re: Basic q regarding STP initial convergence*
> *Roy Waterman * to: Danshtr 08/08/09 04:10 PM
>
> Sent by: *nobody_at_groupstudy.com* Cc: ccielab
> *Please respond to Roy Waterman*
>
>
>
> ------------------------------
>
>
>
> Never mind, after thinking about it I know the answer ;)
> Posted prematurely.
>
> 2009/8/8 Danshtr <danshtr_at_gmail.com>
>
> > What will happen when you boot all your switches at the same time?
> >
> > Best regards,
> > Dan
> >
> >
> >
> > On Sat, Aug 8, 2009 at 4:25 PM, Roy Waterman <roy.waterman_at_gmail.com
> >wrote:
> >
> >> Hi all
> >> In several texts I've read that switches upon convergence each think
> they
> >> are the root bridge AND send config pdus out all ports.
> >> However in Cisco's implementation, with the intial blocking state being
> 20
> >> secs, and having the ability to only receive config pdus from
> neighboring
> >> switches,
> >> while each switch upon initial convergence may THINK they are the root
> >> bridge is it true that in general they do not have a chance to advertise
> >> that as a result of possibly receiving a better bpdu from a neighboring
> >> switch?
> >>
> >> Plus, was the initial 20 sec blocking state proposed by Cisco to
> actually
> >> allow switches enough time to learn the identity of the root bridge
> before
> >> sending bpdus of their own?
> >>
> >> Please advise.
> >>
> >> --
> >> Regards
> >> Roy
> >>
> >>
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> >>
> >
>
>
> --
> Regards
> Roy
>
>
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-- 
Regards
Roy
Blogs and organic groups at http://www.ccie.net