From: Gregory Gombas (ggombas@gmail.com)
Date: Wed Sep 19 2007 - 10:39:59 ART
Hi Rik,
Can you share the configuration commands needed to achieve a 12 second
convergence time?
Thanks
On 9/19/07, Guyler, Rik <rguyler@shp-dayton.org> wrote:
> Well, 50s is the default *maximum* time it will take to transition into the
> forwarding state, not the time it will take.
>
> Taken from your link:
>
> max_age
> = End-to-end_BPDU_propa_delay + Message_age_overestimate
> = 14 + 6
> = 20 sec
>
> 2 x forward_delay
> = end-to-end_BPDU_propagation_delay + Message_age_overestimate +
> Maximum_frame_lifetime + Maximum_transmission_halt_delay
> = 14 + 6 + 7.5 + 1 = 28.5
>
> forward_delay
> = 28.5 /2
> = 15 (rounded)
>
>
> So the maximum time it would take to transition into the forwarding state by
> default is:
>
> max_age + 2 x forward_delay = 50sec (rounded)
>
> To answer Gary's question, if all you adjusted was max_age and forward_delay
> then you're right, 14 seconds would be the minimum you could achieve. To
> get below that number you will have to adjust either the the hello interval
> or diameter. Here's the formula:
>
> End-to-end_BPDU_propa_delay
> = ((lost_msg + 1) x hello) + ((BPDU_Delay x (dia - 1))
> = ((3 + 1) x hello) + ((1 x (dia - 1))
> = 4 x hello + dia - 1
> = 4 x 2 + 6
> = 14 sec
>
> Message_age_overestimate
> = (dia - 1) x overestimate_per_bridge
> = dia - 1
> = 6
>
> Maximum_frame_lifetime
> = dia x transit_delay + med_access_delay
> = dia + 0.5
> = 7.5
> = 8 (rounded)
>
> Maximum_transmission_halt_delay
> = 1
>
> Rik
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> alexey
> Sent: Wednesday, September 19, 2007 7:56 AM
> To: davidytk
> Cc: ccielab@groupstudy.com
> Subject: Re: STP and Routing questions
>
> 2007/9/19, davidytk <davidytk@netvigator.com>:
> >
> > Default the STP port from blocking to fowarding is 50s.
>
>
> Don't agree!
> http://cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00800949
> 54.shtml
>
> "...The movement of a port into the listening state indicates that there is
> a change in the active STP topology and that a port will go from blocking to
> forwarding."
>
> For a definition of these changes is Max Age. But two timer Forward Delay
> responsible for the transition from BLK to FWD!
>
>
> This timer is
> > related to forward delay and max age
> >
> > 50s = 2*forward delay + max age.
> >
> > Default forward delay = 15s
> > Default max age = 20s
> >
> > I think the question is related to this item. But there is some other
> > ways to minimum the timer.
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of alexey
> > Sent: Wednesday, September 19, 2007 5:53 PM
> > To: ccielab@groupstudy.com
> > Subject: Fwd: STP and Routing questions
> >
> > > 1. What about max age time? The minimum max age is 6 seconds.
> > > Minimum forward delay is 4 seconds.
> > >
> > > So 6+(4*2) = 14 seconds is the minimum, isn't it?
> > >
> > > Someone please verify these numbers...
> >
> >
> > This is not true. Because the question specifically about port startup
> > (BLK
> > -> FWD), rather than on the time of convergence network (Max Age +
> > -> Forward
> > Delay + Forward Delay).
> >
> >
> > > On 9/17/07, hadek.el-ayachi@nsn.com <hadek.el-ayachi@nsn.com> wrote:
> > > > Hi Experts,
> > > > I have the following questions:
> > > > 1- In a non root switch, make the startup time of ports in vlan 15
> > > > equal to 12 seconds?
> >
> >
> > All changes timers should be done only at the root switch. Changes
> > timers at non-root switches will not lead to any results. Am I right?
> >
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