From: Dave Temkin (dave@ordinaryworld.com)
Date: Mon Oct 24 2005 - 20:13:39 GMT-3
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
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
> --
> No virus found in this incoming message.
> Checked by AVG Anti-Virus.
> Version: 7.0.344 / Virus Database: 267.12.4/146 - Release Date: 21/10/2005
>
> --
> No virus found in this outgoing message.
> Checked by AVG Anti-Virus.
> Version: 7.0.344 / Virus Database: 267.12.4/146 - Release Date: 21/10/2005
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
> --
> No virus found in this incoming message.
> Checked by AVG Anti-Virus.
> Version: 7.0.344 / Virus Database: 267.12.4/146 - Release Date: 21/10/2005
>
> --
> No virus found in this outgoing message.
> Checked by AVG Anti-Virus.
> Version: 7.0.344 / Virus Database: 267.12.4/146 - Release Date: 21/10/2005
>
> _______________________________________________________________________
> Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Sun Nov 06 2005 - 22:00:52 GMT-3