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 <[email protected]> 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 > >
