BGP TTL

Andrew Partan post-ptomaine at partan.com
Wed Mar 20 20:07:20 UTC 2002


On Wed, Mar 20, 2002 at 11:55:50AM -0800, Aditya wrote:
> > I.e.: set TTL to 1 and your route only goes to your neighbors.
> ie. community no-export

Only if your neighbor listens to communities & does not strip any
that they recieve.  [Someone at lunch mentioned one ISP that wanted
a guarentee that their neighbor would not propogate some routes &
did not want to rely on setting no-export as that breaks too often.]

> so could you give an example where you wouldn't use community no-export nor a
> pre-agreed upon community between multiple AS (neighbors and their neighbors)
> that this would be useful? 

You can use communities and cooperative configuration to make nearly
anything work.  However this is not the case fairly often in
practice.

You can attempt to get this done via cooperation and try to enforce
this by checking route-servers and adding Ts&Cs to contracts, but
it sure would be a lot easier if the protocol just did it.  Its
also a lot harder to get cooperation more than 1 AS hop away
(assuming that you know all of those folks).

	--asp



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