bgp route dampening / ip event dampening

Hi John,

You may wish to investigate BGP Route Dampening:

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Route flap dampening won't give you the shut down that prevents the neighbors from flapping in the first place.

IP Event Dampening is a feature based on the BGP route flap dampening code:

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IP Event Dampening will shut the interface if it flaps too many times and hold it down as long as it continues to flap.

This will prevent BGP from even attempting to form a peering relationship.

The user guide and the parameters are very hard to understand.

Want to block a crashed router for 10 minutes:

dampening [half-life-period reuse-threshold] [suppress-threshold max-suppress [restart-penalty]]

How to work out the values:

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Hope this helps.

Brad Reese BradReese.Com Cisco Repair Service Experts

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Hendersonville Road, Suite 17 Asheville, North Carolina USA 28803 U.S. Toll Free: 877-549-2680 International: 828-277-7272

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G'Day everyone, Wondering if anyone could help me out here. I trying to get my head around this whole dampening thing. I know why you need it, and how to configure it. The only thing I don't know or understand is how to come up with the values (other then the default). Lets take ip event dampening for an example Ok.

Router(config)#interface fa0/0 Router(config-if)#dampening [half-life-period reuse-threshold] [suppress-threshold max-suppress] [restart-penalty] Router(config-if)#end

Now I understand that once an interface flaps it is assigned a penalty of 1000. Half-life period is the time after which the penalty is decreased. The penalty is decreased by half after the half-life period expires. The reuse-threshold is based on the number of penalise. Once the penalty falls below this value the interface is unsuppressed. The suppress-threshold is the value of the accumulated penalties. Once the suppress-threshold is reached the interface(or route) is suppressed. The max-suppress-time is basically the time in seconds the interface can be suppressed (im a little confused with this compared to reuse-threshold). And lastly the restart-penalty is just a value the interface should start with once the router has been rebooted and the interface comes up.

Now with all this said, how does one work all these values out. For example. I have an interface that flaps. I want to dampen that interface if it flaps lets say 3 time in 5 minutes. once it is dampened it should stay dampened for 10 mins. How would I work out these values for this sort of problem. Is there some magic formula ? Its prob very simple but Im just not seeing the light here. Any help would be appreciated.

Regards

John

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