[177181] in North American Network Operators' Group
something strange about bgp community
daemon@ATHENA.MIT.EDU (Song Li)
Wed Jan 7 08:38:18 2015
X-Original-To: nanog@nanog.org
Date: Wed, 07 Jan 2015 21:35:35 +0800
From: Song Li <refresh.lsong@gmail.com>
To: nanog list <nanog@nanog.org>
Reply-To: refresh.lsong@gmail.com
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Hi everyone,
Today when I check one route in Routeviews I find something strange as
follows:
route-views>sh ip bgp 176.108.0.0
BGP routing table entry for 176.108.0.0/19, version 23405621
Paths: (33 available, best #28, table default)
Not advertised to any peer
Refresh Epoch 1
202018 35320 35320 57800
5.101.110.2 from 5.101.110.2 (5.101.110.2)
Origin IGP, localpref 100, valid, external
Community: 702:120 2914:429 20485:52990 20485:53990 20485:54040
20485:54050 47541:10001
rx pathid: 0, tx pathid: 0
the AS-Path is "202018 35320 35320 57800" but the community is 702:120
2914:429 20485:52990 ....
According to RFC 1997, the community format is AA:NN and AA means the
AS#. Here, AS702, AS2914 and AS20485 do not appear in the AS-Path and as
a result they should not appear in the community. Could anybody tell me
what's the reason they do appear in the community of this route?
Thanks!
--
Song Li
Room 4-204, FIT Building,
Network Security,
Department of Electronic Engineering,
Tsinghua University, Beijing 100084, China
Tel:( +86) 010-62446440
E-mail: refresh.lsong@gmail.com
