[177182] in North American Network Operators' Group
Re: something strange about bgp community
daemon@ATHENA.MIT.EDU (Jared Mauch)
Wed Jan 7 09:30:04 2015
X-Original-To: nanog@nanog.org
From: Jared Mauch <jared@puck.nether.net>
In-Reply-To: <54AD3627.7020006@gmail.com>
Date: Wed, 7 Jan 2015 06:29:36 -0800
To: "refresh.lsong@gmail.com" <refresh.lsong@gmail.com>
Cc: nanog list <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
2914:429 is a community to signal to NTT to not announce the route to peers w=
hich would perhaps be why you don't see NTT doing that.=20
You can see the documented NTT communities here: http://www.us.ntt.net/suppo=
rt/policy/routing.cfm
Jared Mauch
> On Jan 7, 2015, at 5:35 AM, Song Li <refresh.lsong@gmail.com> wrote:
>=20
> Hi everyone,
>=20
> Today when I check one route in Routeviews I find something strange as fol=
lows:
>=20
> 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
>=20
> the AS-Path is "202018 35320 35320 57800" but the community is 702:120 291=
4:429 20485:52990 ....
>=20
> 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 resul=
t they should not appear in the community. Could anybody tell me what's the r=
eason they do appear in the community of this route?
>=20
> Thanks!
>=20
> --=20
> 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
