From: Swaroop Potdar (swarooppotdar@hotmail.com)
Date: Sun Jul 17 2005 - 11:13:02 GMT-3
Hi TIm,
Thanks !
Just missed the max half life of 30 seconds.
btw
the half life time starts after the interface is dampened or form the first
penalty;
the doc cd on explanation of the feature has two descriptions for the same
thing
Half-Life Period :
The half-life period determines how fast the accumulated penalty can decay
exponentially. When an interface is "placed in a dampened state " , the
router monitors the interface for additional up and down state changes. If
the interface continues to accumulate penalties and the interface remains in
the suppress threshold range, the interface will remain dampened. If the "
interface stabilizes and stops flapping, the penalty is reduced by half
after each half-life period expires". The accumulated penalty will be
reduced until the penalty drops to the reuse threshold. The configurable
range of the half-life period timer is from 1 to 30 seconds. The default
half-life period timer is 15 seconds.
And this is the syntax description in the same document which matches your
explanation which start from the time penalty is assigned to an interface:
( this seems more like BGP Route dampening description in the DOC CD)
half-life-period:
(optional) Time (in seconds) after which a penalty is decreased. Once the
route has been assigned a penalty, the penalty is decreased by half after
the half-life period expires. The range of the half-life period is from 1 to
30 seconds. The default time is 15 seconds.
So which is the correct ones ???
I do agree that we should move on just understanding how it works , but does
it work the first way or the second way?
>From: "ccie2be" <ccie2be@nyc.rr.com>
>To: "'Swaroop Potdar'" <swarooppotdar@hotmail.com>, <buesink@fma.nl>,
> <ccielab@groupstudy.com>
>Subject: RE: Interface Dampening
>Date: Sun, 17 Jul 2005 09:41:19 -0400
>
>Swaroop,
>
>You must have missed the post from Marvin Greenlee on this.
>
><Quote>
>Dampening for an interface uses a half life value in seconds. With a range
>of 1-30 seconds, the penalty will decay very quickly.
>
>IP Event Dampening
>http://www.cisco.com/en/US/products/sw/iosswrel/ps1838/products_feature_guid
>e09186a0080134a41.html#wp1048359
>
>
>With that in mind, your half life value can be a maximum of 30 seconds.
>
>So, let's say your interface flaps once a minute for the first 6 minutes
>and
>consider the penalty of the first flap over that period.
>
>Also assume that the first flap takes place immediately at T=0.
>
>So, at T=0, the penalty = 1000.
>
>At T=30 in seconds, the penalty = 500
>
>AT T=60, the penalty = 250 plus the penalty for the 2nd flap or 1250.
>
>At T=90, the total penalty = 625.
>
>At T=120, the penalty = 312.5 plus the penalty for the 3rd flap or 1312.5
>
>At T=150, the penalty = 656.25
>
>At T=180, the penalty = 328.125 plus the penalty for the 4th flap or
>1328.12
>
>At T=210, the penalty = 664
>
>At T=240, the penalty = 332 plus the penalty for the 5th flap or 1332.
>
>So, after 4 minutes and 5 flaps, the penalty is only 1332.
>
>You still have a long time to go and many more flaps are needed before you
>reach the suppress threshold of 6000.
>
>Now, look at the total penalty amount at the end of each minute. It starts
>out at 1000. And, you end up with this series:
>
>1000, 1250, 1312, 1328, 1332, etc
>
>Notice how after each minute the difference between the current penalty and
>the previous penalty keeps getting smaller and smaller.
>
>With a maximum half life of 30 seconds and a flap rate of once per minute,
>as you can see, it will take a very long time to reach your suppress
>threshold of 6000.
>
>Since the half life is already set to it's max, the only other variable you
>change is the suppress threshold which would need to be much, much lower.
>
>Given the unlikelihood that cisco would tell you exactly when and how often
>the interface would flap and the time consuming nature of the calculations,
>I highly doubt you would get a task worded that way.
>
>So, my advice is to understand how this works and move on to other topics.
>
>HTH, Tim
>
>
>
>-----Original Message-----
>From: Swaroop Potdar [mailto:swarooppotdar@hotmail.com]
>Sent: Sunday, July 17, 2005 8:03 AM
>To: ccie2be@nyc.rr.com; buesink@fma.nl; ccielab@groupstudy.com
>Subject: RE: Interface Dampening
>
>Hi,
>
>how would be
>
>max-supress of 3600
>supress threshold of 6000
>reuse threshold of 499
>half-time of 900
>
>would this serve the purpose if the interface has to be kept dampned if it
>flaps 6 times in an hour.
>
>????
>
>
> >From: "ccie2be" <ccie2be@nyc.rr.com>
> >Reply-To: "ccie2be" <ccie2be@nyc.rr.com>
> >To: <buesink@fma.nl>, <ccielab@groupstudy.com>
> >Subject: RE: Interface Dampening
> >Date: Thu, 14 Jul 2005 17:35:40 -0400
> >
> >Hi,
> >
> >I'll take a crack at this.
> >
> >Every time the interface flaps, it incurs a penalty of 1000 points (this
> >penalty amount is not configurable).
> >
> >However, you can specify the suppress amount which in your case is at
>least
> >6 x 1000 or 6000 points. (This suppress amount actually has to be lower
> >than
> >6000 because the penalty starts to decay immediately.)
> >
> >But, you're not done yet. Once a penalty occurs, it starts to decay at a
> >rate of 1/2 the penalty amount per half life. In other words, if the
>half
> >life is 30 minutes, 30 minutes after the penalty occurs, the penalty is
> >only
> >500 points.
> >
> >So, now the problem is to figure out how to get to a penalty of 6000 with
>6
> >flaps in an hour. If there weren't this penalty decaying aspect, this
> >would
> >be easy. But, with this decaying aspect, the answer depends on when
>within
> >the first hour the flaps occur.
> >
> >If all 6 flaps occur in the last minute of the hour than there won't be
> >much
> >time for the penalty to decay much so if your suppress level is should be
> >something like this:
> >
> >total penalties - decay amount > suppress level
> >
> >So, in your case, total penalties is 6000. Decay amount depends on half
> >life where the greater the half-life, the smaller the decay amount. So,
>if
> >you set the suppress level to 5001 and set a very large half you should
>be
> >OK.
> >
> >HTH, Tim
> >
> >
> >-----Original Message-----
> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> >buesink@fma.nl
> >Sent: Thursday, July 14, 2005 4:49 PM
> >To: ccielab@groupstudy.com
> >Subject: Interface Dampening
> >
> >Hi there,
> >
> >I've a question, I'm playing with interface dampening.
> >And I am always messing things up with it ;-)
> >
> >I want to do the following:
> >
> >If an interface flaps 6 times within an hour, then I want to dampen it.
> >
> >How can I set this up?
> >
> >
> >Regards!
> >
> >_______________________________________________________________________
> >Subscription information may be found at:
> >http://www.groupstudy.com/list/CCIELab.html
> >
> >_______________________________________________________________________
> >Subscription information may be found at:
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>
>
>Regards,
>Swaroop.
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Regards,
Swaroop.
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