Flapping prefixes and dialup networks. Discuss.


I sent a network provider (who shall remain protected
by a pseudonym like "AS 174") a brief note stating that
they had a prefix that was flapping rather heavily
throughout the day.

I cut and pasted a show ip bgp on the route, pointing out
that the prefix flaps on the order of once a minute and was
happily being dampened. (cf. my comments Monday afternoon on

BGP routing table entry for, version 656911
Paths: (2 available, no best path)
  1239 174 (history entry) (metric 15) from (
      Origin IGP, metric 1, localpref 90, external
      Dampinfo: penalty 2915, flapped 199 times in 3:27:31
  1239 174 (history entry) (metric 15) from (
      Origin IGP, metric 1, localpref 90, external
      Dampinfo: penalty 2917, flapped 198 times in 3:27:07

I also asked this nameless service provider to kindly check
into this somewhat excessive amount of flap with a view to
seeing how it could be made to flap less.

Here was the reply.

Hopefully saner and more patient folks than me might point
out to service provider X that announcing to the entire
world when a dialup user comes and goes is not healthy for
the Internet, and it shouldn't happen, particularly not at
this rate.

Why I am not quite in the, "it doesn't matter, they'll
be dampened" frame of mind will get explained during
the NANOG session.

- --

Aaron, have you never heard of aggregation? Can't you aggregate this
customer's route with other /24's and thus hide their comings and goings
from the entire global Internet. Can you imagine what would happen if
every dialup network in the world announced itself every time it logged
in or out of it's service provider?

This is not only anitsocial behaviour on the part of PSI, but you are in
effect, holding your customer up to ridicule before the world by
announcing their every coming and going. IMHO this is an extremely poor
attitude to have towards your customers.

Michael Dillon Voice: +1-604-546-8022
Memra Software Inc. Fax: +1-604-542-4130
http://www.memra.com E-mail: michael@memra.com