Not only do /24's run amuk...

...They seem to come & go as they please!

Inspired by RAS's prior posts regarding /16's that were hastly de-agged, I
took some time this weekend to answer a few questions which came up; how
many updates do I hear about a specific prefix, and does the length have any
relationship? Well, several hours later, I knew pretty straight away how
many updates I heard about various prefixes in the STS Telecom looking
glass, at least.

Consider this v0.0.1-alpa of the "Most-Heard Prefix" list, a sort of
web-based and rule-less implementation of 'sh ip bgp flap-statistics.'

The sorted list, updated every 60 minutes, is available here in gzip format
due to excessive size (indeed, 10 peers act as a amplifier):

Incidently, many of the most-updated prefixes are included in the list of
RAS's /16 de-aggs.

Todo: ignore the effects of a peer session resets (i.e. don't consider a
reload as part of the per-prefix flap count) and look at path changes with
each update (is it a normal flap, or mid-day traffic-engineering session
gone wrong?).

Any comments or suggestions for changes are very welcome; please reply



Hi Anton,
I suppose its to be expected that smaller blocks will flap more than larger
ones if you consider that if I have a /8 I'm likely injecting the /8 into BGP
from a lot of core routers and so its unlikely that I'll have a problem which
takes out enough routers for my route to withdraw, by contrast I'd expect a /24
to be sourced from probably a single point and hence be affected by any issue at
that particular PoP,

just my 2-euros :slight_smile: