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Re: dampening posted 08/30/2006
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Victor,
 the formula is just derived by the simple statement "Current penalty halves every HLife time":
 
 Assume that at time t=0 CurrentPenalty is equal to StartPenalty
 
 at time t = HLife the CurrentPenalty is: StartPenalty/2
 at time t = 2 * HLife the CurrentPenalty is StartPenalty/4 (= StartPenalty/(2^2))
 
 at time t = n * HLife the CurrentPenalty is StartPenalty/2^n
 
 Then:
 
 CurrentPenalty(nHLife) = StartPenalty/2^n = StartPenalty * 2^ (-n)
 
 calling "t = nHLife" => n = t/HLife
 
 Finally:
 
 CurrentPenalty(t) = StartPenalty * 2 ^(-t/Hlife)
 
 
 Sabrina
 

----- Original Message ----
From: Victor Cappuccio <cvictor@xxxxxxxxxxxxxxxxx>
To: Bobby <aggiebob98@xxxxxxxxx>; "Moin, Imran" <imoin@xxxxxxxxxxx>; Sami <sy1977@xxxxxxxxx>
Cc: ccielab@xxxxxxxxxxxxxx; Petr Lapukhov <petr@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Tuesday, August 29, 2006 2:25:01 PM
Subject: RE: dampening

Hi Bobby 
 
So Ok it would be 1000 in the first flap, but I would NOT have 1000 as the
current Penalty value
 
R1(config-if)#do show int f0/0 damp        
FastEthernet0/0 
  Flaps Penalty    Supp ReuseTm   HalfL  ReuseV   SuppV  MaxSTm    MaxP
Restart
      1     629   FALSE       0      15    1000    3000      60   16000
0
R1(config-if)#
*Mar  4 16:45:43.553: EvD(FastEthernet0/0): accum. penalty decayed to 629
after 10 second(s)
 
I wish to know where did Petr got this formula I been browsing High and Low
for this 
"CurrentPenalty = StartPenalty*2^(-t/HLife) (it halves every HLife time)"
but with out luck.
 
Sorry I could not give more help about this
 
Regards
Victor.-
 
 
 
 
 
 

 

 

 

  _____  

De: Bobby [mailto:aggiebob98@xxxxxxxxx] 
Enviado el: Martes, 29 de Agosto de 2006 04:51 p.m.
Para: Victor Cappuccio; 'Moin, Imran'; 'Sami'
CC: ccielab@xxxxxxxxxxxxxx; 'Petr Lapukhov'
Asunto: RE: dampening

 

I would have though the correct answer to be 15 1000 3000 60 to be the
correct answer since the first value is the 1/2 half of the period specified
and the third represents how much penalty it would take to suppress it (it
is always penalized by 1000)

 

Bobby

Victor Cappuccio <cvictor@xxxxxxxxxxxxxxxxx> wrote:

Hi Moin,

The explanation was done by Petr Lapukhov he is an Internetwork Expert
Instructor, so the credit of the explanation belongs to him. I'm CCying him
to see if he has more about this.

Now I will be very careful reading the requirements since the Reuse value
has a default of 1000, so the route is unsuppressed and made available to
the other devices on the network

I think that 30 1000 2001 100 is another way to accomplish the 3 or more
flaps in 30 sec question. Just play around using deb dampening all shutting
down the interface and no shutting it back and let me know your results :D

Thanks!
Victor.-



-----Mensaje original-----
De: Moin, Imran [mailto:imoin@xxxxxxxxxxx] 
Enviado el: Lunes, 28 de Agosto de 2006 11:50 p.m.
Para: Victor Cappuccio; Sami
CC: ccielab@xxxxxxxxxxxxxx
Asunto: RE: dampening

Victor,

Good explanation. If the question states that the interface needs to be
withdrawn from the routing table if there are 3 or more flaps in 30
secs, then I guess the most important thing to decide is when to
suppress the interface. With only these requirements, will these values
work?

Half-life Time = 30 secs
Value to start reusing the interface - Doesn't matter, does it?
Value to start suppressing an interface = 2000
Max duration to suppress an interface = doesn't matter, does it?


Thanks,
Imran.

-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Victor Cappuccio
Sent: Thursday, July 27, 2006 2:20 PM
To: 'Sami'
Cc: ccielab@xxxxxxxxxxxxxx
Subject: RE: dampening

Sami,

Some good links
http://www.groupstudy.com/archives/ccielab/200603/msg00204.html

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft
/120
limit/120s/120s22/s_ipevdp.htm#wp1027177

The answer for your question:
dampening 30 1500 2000 100

And some outputs from a Router.

To resume the output below
1st Flap at Jul 27 00:14:58.985 penalty 1000, flap count 1 2nd Flap at
Jul 27 00:15:11.125 penalty 1755, flap count 2, Diff 1st Flap & 2nd Flap
almost 13s 3er Flap at Jul 27 00:15:23.614 penalty 2331, now suppressed
with a reuse intervals of 20 12 from a amount of 25 sec.

R2(config-if)#do show run int s0/0 | in damp

dampening 30 1500 2000 100

R2(config-if)#s

R2(config-if)#

Jul 27 00:14:58.985: IF-EvD(Serial0/0): IP Routing reports state
transition from UP to DOWN
========================================================================
====
Jul 27 00:14:58.985: EvD(Serial0/0): charge penalty 1000, new accum.
penalty 1000, flap count 1
========================================================================
====
Jul 27 00:14:58.985: EvD(Serial0/0): accum. penalty 1000, not suppressed
========================================================================
====
Jul 27 00:14:58.985: IF-EvD(Serial0/0): update IP Routing state to DOWN,
interface is not suppressed
========================================================================
====

R2(config-if)#s
R2(config-if)#
========================================================================
====
Jul 27 00:15:11.125: IF-EvD(Serial0/0): IP Routing reports state
transition from UP to DOWN
========================================================================
====
Jul 27 00:15:11.125: EvD(Serial0/0): accum. penalty decayed to 757 after
12
second(s)
========================================================================
====
Jul 27 00:15:11.125: EvD(Serial0/0): charge penalty 1000, new accum.
penalty 1757, flap count 2
========================================================================
====
Jul 27 00:15:11.125: EvD(Serial0/0): accum. penalty 1757, not suppressed

========================================================================
====
R2(config-if)#s
R2(config-if)#
========================================================================
====
Jul 27 00:15:23.614: IF-EvD(Serial0/0): IP Routing reports state
transition from UP to DOWN
========================================================================
===
Jul 27 00:15:23.614: EvD(Serial0/0): accum. penalty decayed to 1331
after 12
second(s)
========================================================================
===
Jul 27 00:15:23.614: EvD(Serial0/0): charge penalty 1000, new accum.
penalty 2331, flap count 3
========================================================================
====
Jul 27 00:15:23.614: EvD(Serial0/0): accum. penalty 2331, now suppressed
with a reuse intervals of 20, ::::: THE INTERFACE IS SUPPRESSED::::
========================================================================
====
Jul 27 00:15:23.614: IF-EvD(Serial0/0): update IP Routing state to DOWN,
interface is suppressed R2(config-if)# Jul 27 00:15:25.613:
%LINK-5-CHANGED: Interface Serial0/0, changed state to administratively
down R2(config-if)#n Jul 27 00:15:25.613: IF-EvD(Serial0/0): IP Routing
reports state transition from DOWN to DOWN Jul 27 00:15:26.614:
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0,changed state
to down Jul 27 00:15:26.614: IF-EvD(Serial0/0): IP Routing reports state
transition from DOWN to DOWN R2(config-if)#n R2(config-if)# Jul 27
00:15:26.815: IF-EvD(Serial0/0): IP Routing reports state transition
from DOWN to UP R2(config-if)# Jul 27 00:15:28.814: %LINK-3-UPDOWN:
Interface Serial0/0, changed state to up R2(config-if)# Jul 27
00:15:28.814: IF-EvD(Serial0/0): IP Routing reports state transition
from UP to UP Jul 27 00:15:28.814: IF-EvD(Serial0/0): IP Routing reports
state transition from UP to UP Jul 27 00:15:29.816: %LINEPROTO-5-UPDOWN:
Line protocol on Interface Serial0/0, changed state to up Jul 27
00:15:29.816: IF-EvD(Serial0/0): IP Routing reports state transition
from UP to UP

HTH
Victor.-



-----Mensaje original-----
De: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] En nombre de
Sami Enviado el: Miircoles, 26 de Julio de 2006 06:03 p.m.
Para: ccielab
Asunto: dampening

Group,

One of the task say ..3 interfcae flaps in 30 second will keep interface
participating in routing...Is this correct ?

dampening 30 1000 2000 120..

Thanks

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