BGP Path Filtering
Iljitsch van Beijnum
iljitsch at muada.com
Sat May 17 18:59:59 UTC 2003
On zaterdag, mei 17, 2003, at 17:30 Europe/Amsterdam, Joe Abley wrote:
> think that the message "community strings are hard" (like its friends
> "BGP is hard" and "let's turn on RIP") need to stop propagating. It is
> just not that difficult to do things right the first time, and you
> don't need to be a bigger network than a pair of 2501s with a small
> handful of external BGP sessions to see the benefit of it.
You are saying BGP isn't hard when well-informed people can't even
agree on a way to disable unwanted default behavior? Hm...
Filtering AS paths and prefixes is relatively well understood, although
I hear lots of people fail the CCIE questions on AS path regular
expressions. I wouldn't recommend doing it with communities to people
who don't have any experience with route maps. And I don't see the
point for people who don't have BGP-speaking customers. Apart from that
it's mostly a change management issue. The communities mechanism has
the advantage you only have to make changes on the routers where the
prefixes enter the network (presumably a single customer-facing router)
while explicit filters must be updated on all eBGP routers.
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