From: Scott Morris (smorris@ipexpert.com)
Date: Wed Sep 19 2007 - 11:20:33 ART
Convergence time does not include the blocking timer (20 sec) so it's just 2
x forward-time. (listen + learn)
Therefore, set your spanning-tree forward-time to 6 and you'll get 12 second
convergence and 32 second initial delay when first connecting to the switch.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
smorris@ipexpert.com
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Gregory Gombas
Sent: Wednesday, September 19, 2007 9:40 AM
To: Guyler, Rik
Cc: alexey; davidytk; ccielab@groupstudy.com
Subject: Re: STP and Routing questions
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_note09186a00
> 800949
> 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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