What's the point of prepend communities?
Leo Bicknell
bicknell at ufp.org
Mon Oct 30 17:24:11 UTC 2017
In a message written on Thu, Oct 26, 2017 at 01:54:17PM -0600, Clinton Work wrote:
> I believe that Jason is asking about an ISP BGP community to prepend
> their AS when the BGP routes are received from the customer (not when
Yeah, I typoed my example, should have been:
There are paths:
1 2 3 5
1 2 4 5
If you prepend your ASN, you get:
1 1 2 3 5
1 1 2 4 5
No difference. If you send the ISP a prepend community for 3, you get:
1 2 2 3 5
1 2 4 5
And you just forced all traffic to the second, shorter path. For only
customers that are dual homed to 3 & 4 without affecting other traffic.
--
Leo Bicknell - bicknell at ufp.org
PGP keys at http://www.ufp.org/~bicknell/
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