From: Thomwin Chen (thomwin_chen@yahoo.com)
Date: Sat Oct 29 2005 - 10:34:37 GMT-3
oops sorry,
I just noticed that it's already been answered by Simon :)
Dave Temkin <dave@ordinaryworld.com> wrote:
Which one, Simon or me? :-)
-Dave
On Sat, 29 Oct 2005, The Great Ryan wrote:
> Hi, CCIE, How are you ?
>
> =)
>
> Ryan
>
> 2005/10/25, simon hart :
> > No, that would be 30 / 2000
> >
> > Simon
> >
> > -----Original Message-----
> > From: Dave Temkin [mailto:dave@ordinaryworld.com]
> > Sent: 25 October 2005 00:14
> > To: simon hart
> > Cc: Milenko Markov; ccielab@groupstudy.com
> > Subject: RE: Route Dampening
> >
> >
> > OK, so let's say it's 3 flaps in 30 seconds... How does the calculation
> > work then? 30/3000?
> >
> >
> > On Mon, 24 Oct 2005, simon hart wrote:
> >
> > > Hi Milenko,
> > >
> > > You bring up some fascinating points with regards to this suppression
> > > question. However I believe the question related to interface dampening
> > as
> > > opposed to BGP dampening, thus the times are expressed in seconds rather
> > > than minutes, thus the rate at which the penalty decreases is far more
> > rapid
> > > (however the overall philosophy still holds).
> > >
> > > So if we take the worst case scenario, do we use a suppress of 3000 ?? If
> > > so the interface would be dampened after 4 flaps and not 5. Anything used
> > > as a suppress-threshold of less than 4000 will mean the interface could
> > get
> > > dampened after 4 flaps!!!, But also means that the interface could
> > > potentially not get dampened after 30 seconds.
> > >
> > > And you are right regarding the reuse threshold, in the example I gave
> > there
> > > is potential for the route to get unsurpressed within that 30 second
> > period.
> > > However the question does not state how long it should be surpressed for,
> > so
> > > becoming unsurpressed within 30 seconds should not be an issue.
> > >
> > > My conclusion is that it is impossible to answer this question with values
> > > that will meet every criteria for flapping. If I had this question in the
> > > lab, I think I would argue the point with the proctor.
> > >
> > > I think the question would only make sense if it was geared to 2 flaps in
> > 30
> > > seconds or 3 flaps in 30 seconds.
> > >
> > > More thoughts ?????
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > > Milenko Markov
> > > Sent: 24 October 2005 21:44
> > > To: 'simon hart'
> > > Cc: ccielab@groupstudy.com
> > > Subject: RE: Route Dampening
> > >
> > >
> > > Simon,
> > >
> > > lets observe "worst case scenario" (?) : 4 flaps "in" first second, and 1
> > > flap in last (30').
> > >
> > > Penalty would be (4x1000/2)+1000=3000...route would not be suppressed ?
> > >
> > > I *think* that here two more values playes their role (marked with *) :
> > >
> > > 1. "Half-life-Once the route has been assigned a penalty, the penalty is
> > > decreased by half after the half-life period (which is 15 minutes by
> > > default). The process of reducing the penalty happens every *5 seconds*."
> > >
> > > and
> > >
> > > 2. " Reuse limit-As the penalty for a flapping route decreases and falls
> > > below this reuse limit, the route is unsuppressed. That is, the route is
> > > added back to the BGP table and once again used for forwarding. The
> > default
> > > reuse limit is 750. The process of unsuppressing routes occurs at
> > > *10-second* increments. Every 10 seconds, the router finds out which
> > routes
> > > are now unsuppressed and advertises them to the world."
> > >
> > >
> > >
> > http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fipr
> > > _c/ipcprt2/1cfbgp.htm#wp1002395
> > >
> > >
> > > more ideas ?
> > >
> > > regards,
> > > Milenko.
> > >
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> > > simon hart
> > > Sent: 24. oktobar 2005 22:31
> > > To: Charles Cahoon; ccielab@groupstudy.com
> > > Subject: RE: Route Dampening
> > >
> > > Charles,
> > >
> > > You will get a penalty of 1000 for each flap. Your half-life will default
> > > to 30 seconds (best to leave it there).
> > >
> > > You need to work out what to suppress at
> > >
> > > If you flapped immediately 5 times in the first couple of seconds you will
> > > get a penalty of 5000, however a figure of 5000 does not work in the
> > > following scenario:-
> > >
> > > If you flapped 2 times in the first second = 2000 and then flapped 3 times
> > > in the last couple of seconds you will get a penalty of
> > >
> > > roughly 2000/2 = 1000 + 3000 Therefore you will need a
> > suppress-threshold
> > > of 4000 or above, but below 5000
> > >
> > > I would probably go for 4001 - any comments on this figure appreciated.
> > >
> > > So
> > > Half-life = 30
> > > Suppress-threshold = 4001
> > > Reuse-threshold = Arbitary for this exercise, however I would go with
> > Cisco
> > > recommendation of suppress-threshold = reuse*2, therefore 2000
> > > Max-suppress = leave at default (60)
> > >
> > > Simon
> > >
> > > -----Original Message-----
> > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> > > Charles Cahoon
> > > Sent: 24 October 2005 20:30
> > > To: ccielab@groupstudy.com
> > > Subject: Route Dampening
> > >
> > >
> > > Looking for a simple explanation,
> > >
> > > I have read a great deal about how to dampen but it's not getting any
> > > clearer
> > > for me. I was hoping that someone can help.
> > >
> > > My question is if I want to remove a route if it flaps 5 times in 30
> > > seconds?
> > >
> > > Using the "Half-Life, Suppress Threshold, Reuse Threshold and Maximum
> > > Suppress
> > > time" not sure these correlate, what am I missing?
> > >
> > > Thanks for the help
> > >
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