From: Leigh Harrison (ccileigh@gmail.com)
Date: Mon Oct 24 2005 - 17:13:58 GMT-3
Hey Charles,
The half life is the time in which it will cut it's penalty number in half.
It'll then reuse when you tell it what number to reuse at (the reuse
threshold)
The max surpress is when it gives it a second chance, regardless of the
number of the penalty.
The default panalty for a flap is 1000.
dampening HL RT ST MS
HL = half life
RT = reuse threshold
ST = supress threshold
MS = mas surpress
if you wanted to take the link out of routing for 5 flaps in 30 seconds,
then you would put the half-life to 30 seconds (or more) and put yout
surpress threshold to 5000 (or lower).
When you get your 5 flaps - you penalty hits 5000 dropping the link out
of play. You then need to think about when you want him back in and
that's where the tuning of the half-line ans the reuse threshold come in.
The max surpress is used if you get 10 flaps in the first 5 seconds for
example. It may sopt flapping after that, but may take ages to come
back under the reuse threshold - the max-surpress would bail him out
after x seconds.
For interfaces the values are in seconds, but for bgp dampening it is in
minutes.
There is a good diagram here:-
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122s/122snwft/release/122s14/fsipevdp.htm
Hope this helps a bit - to get my head around it, I worte a spreadsheet
to emulate the graph on the website above (yeah, sad, I know) and had a
fiddle with the numbers.
LH
Charles Cahoon wrote:
>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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