I have a client who need to implement BGP flap-dampening in order to
avoid CPU hits on both their border routers and their iBGP DMZ routers
(the iBGP routers seem to be taking the biggest hits), but who don't
want to suppress routes for a long period of time due to their business
model (i.e., they're willing to trade -some- stability in exchange for
content availability). In the past, I've generally employed a graded
flap-dampening model dependent upon prefix-length, dampening larger
blocks for as little as 15 minutes, and smaller nets for as long as an
hour.
So, I'd be grateful for comments concerning border metrics somewhat like
this:
bgp dampening 3 750 2000 7
Is this going to provide a reasonable degree of protection against CPU
spikes caused by rapidly-flapping routes, and/or is it going to cause
unwanted secondary effects due to the greater frequency of
de-suppression? And does it make sense to do dampening on the iBGP DMZ
routers as well as the border, given that 100% of the flapping routes
are external?
Comments/advice/experiences greatly appreciated.
-- ------------------------------------------------------------ Roland Dobbins <mordant@gothik.org> // 408.859.4137 voice
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