From: Jon Mitchell (no email)
Date: Thu May 01 2003 - 12:32:58 EDT
On Wed, Apr 30, 2003 at 12:34:07PM -0400, Kai Schlichting wrote:
> In unrelated news: can someone explain to me the exact meaning of multiple
> AS numbers enclosed in {}'s (or []'s as far as RIS RIPE's display is
> concerned) at the end of the AS path?
>
> * 162.33.64.0/19 207.246.129.6 0 11608 2914 3356 14390 {22714,27481} i
> * 4.0.4.90 1080 0 1 701 14390 {22714,27481} i
> * 203.194.0.5 0 9942 1 701 14390 {22714,27481} i
> * 192.205.31.33 0 7018 3356 14390 {22714,27481} i
> * 195.66.224.82 31502 0 4513 3356 14390 {22714,27481} i
> * 216.140.2.59 981 0 6395 3356 14390 {22714,27481} i
>
This means the address space was aggregated by a different AS than
originated it, for instance parts of 162.33.64.0/19 were originated by
AS 22714 and 27481, but AS 14390 aggregated these to the prefix above. By
using the AS_SET notation, one can prevent the loss of origination AS
information allowing loop avoidance.
-Jon
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