[c-nsp] prefix lists updates and max prefix filters

Mack McBride mack.mcbride at viawest.com
Thu Dec 8 13:41:14 EST 2011

We have pretty good route-maps and we still wind up changing them every so often.
Most of these changes relate to adding additional community translations for things
received from customers and sent to upstreams.

So having a second level of filtering is still a good idea.

Of course we have gotten most of our upstreams to filter on a route registry.
We still have a couple that are manual updates.


-----Original Message-----
From: Gert Doering [mailto:gert at greenie.muc.de] 
Sent: Thursday, December 08, 2011 11:36 AM
To: Mack McBride
Cc: Pete Templin; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] prefix lists updates and max prefix filters


On Thu, Dec 08, 2011 at 09:54:54AM -0800, Mack McBride wrote:
> I should have said not filtering with a prefix list is not really an answer.
> Any time the route-map has to be changed you can and often do get leakage.

There is no need to ever change that route-map.  Which is the great thing about this scheme :-)

> Therefore you need a second method of filtering.


> The upstream should also be filtering.


> <rant> If everyone used route registries to generate prefix lists and 
> kept them up to date this wouldn't be as much of an issue. </rant>
> Thankfully with IPv6 most ASNs will only have one prefix and most of 
> these issues are significantly reduced.  Ie. The prefix list at this point has a maximum of 7K entries.

True, but IPv6 won't magically make those lazy upstreams start filtering their downstreams.  Even if it's less lines of auto-generated prefix lists.

USENET is *not* the non-clickable part of WWW!
Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de

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