On Apr 27, 2009, at 2:20 PM, Jack Bates wrote:

Jonathan Park wrote:

...

Hello all, I was wondering how many of you use route flap dampening in your network. If you have it enabled, what is the main reason?

We've been considering it after the last flap around the world; perhaps with extremely short penalty times.

<http://www.ripe.net/ripe/meetings/ripe-43/presentations/ripe43-routing-flap....

-- TTFN, patrick

We're using Cisco 6509 MSFC2s for core engines with three 85% route feeds and Cisco-default route flap suppression. Yeah, the default flap suppression parameters are aggressive but we want to be sure we don't hog precious CPU cycles from a nasty route flap and provide more consistent routes to our downstreams. We can't take a full route table (232k) due to TCAM limitations, so we have default routes anyway. There's only a subtle impact to our customers with maybe a less preferable, stable path versus a better, flapping one. A better bargain in our book, but maybe not for others... CPU runs around 10-12% all day. If we had more router CPU and no default routes, we'd probably have dampening enabled but at very high thresholds under similar network policies. -D On Mon, Apr 27, 2009 at 2:35 PM, Jack Bates <jbates@brightok.net> wrote:

Patrick W. Gilmore wrote:

...

On Apr 27, 2009, at 2:20 PM, Jack Bates wrote:

...

We've been considering it after the last flap around the world; perhaps with extremely short penalty times.

<http://www.ripe.net/ripe/meetings/ripe-43/presentations/ripe43-routing-flap.pdf>

Yeah, read the presentation several times, thus the short penalty times, and probably high thresholds.

The idea for me is to limit the harm of excessive flapping while not being paranoid. I've had a customer lose a lot of connectivity for 30 minutes after 3 or 4 flaps. I figure 5 minute ignore after about 10 flaps in a  10 minute period.

Jack