[176671] in North American Network Operators' Group
What can I infer from "show ip route" and similar BGP commands?
daemon@ATHENA.MIT.EDU (Reza Motamedi)
Mon Dec 8 22:10:42 2014
X-Original-To: nanog@nanog.org
From: Reza Motamedi <motamedi@cs.uoregon.edu>
Date: Mon, 8 Dec 2014 15:48:21 -0800
To: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
Hello NANOG,
I=E2=80=99m a researcher and I was trying to understand the data I collecte=
d from
some BGP Looking Glasses. Basically, I was hoping to see if BGP records can
tell me where my university=E2=80=99s provider (AS3701) is peering with its
providers. I issued two BGP queries to Level3=E2=80=99s LGs, one in Seattle=
and one
in Amsterdam for my school=E2=80=99s prefix. My strong guess was that our p=
rovider
(AS3701) peers with Level3 in Seattle. I was hoping to conclude something
like this: if the peering occurs in Seattle, the Seattle LG should reveal
it, but Amsterdam should not.
AS3701 is Nero (Network for Education and Research in Oregon) which I
assume is a small regional AS. I don't think Nero peers with Level3 in
Amsterdam, however, I get this AS for my next hop even when I issue the
command from Amsterdam. On the other hand =E2=80=9Ccar1.Sacramento1=E2=80=
=9D suggests that
the peering happens in Sacramento.
This result makes me think what I get is from a combination of iBGP and
eBGP, which is also apparent from =E2=80=9CInternal/External=E2=80=9D keywo=
rds in the data.
My main issue is that the keywords are not always available. In some other
LG I just get a next hop IP and an AS path. How can I make sure that the
peering information comes from an eBGP peering? I think the next hop IP
might be the answer, right?
I included the results of the command for both LGs here, hopefully somebody
could explain to me
-------------------------------------------------
Route results for 128.223.0.0/16 from Amsterdam, Netherlands
BGP routing table entry for 128.223.0.0/16
Paths: (2 available, best #1)
3701 3582
AS-path translation: { OREGONUNIV UONET }
car1.Sacramento1 (metric 58341)
Origin IGP, metric 0, localpref 100, valid, internal, best
Community: North_America Lclprf_100 Level3_Customer United_States
Sacramento
Originator: car1.Sacramento1
3701 3582
AS-path translation: { OREGONUNIV UONET }
car1.Sacramento1 (metric 58341)
Origin IGP, metric 0, localpref 100, valid, internal
Community: North_America Lclprf_100 Level3_Customer United_States
Sacramento
Originator: car1.Sacramento1
-------------------------------------------------
Route results for 128.223.6.81/16 from Seattle, WA
BGP routing table entry for 128.223.0.0/16
Paths: (4 available, best #3)
3701 3582
AS-path translation: { OREGONUNIV UONET }
4.53.150.46 from 4.53.150.46 (ptck-core1-gw.nero.net)
Origin IGP, localpref 90, valid, external
Community: North_America Lclprf_90 Level3_Customer United_States Seattle
Level3:11847
3701 3582, (received-only)
AS-path translation: { OREGONUNIV UONET }
4.53.150.46 from 4.53.150.46 (ptck-core1-gw.nero.net)
Origin IGP, localpref 100, valid, external
Community: Level3:90
3701 3582
AS-path translation: { OREGONUNIV UONET }
car1.Sacramento1 (metric 34363)
Origin IGP, metric 0, localpref 100, valid, internal, best
Community: North_America Lclprf_100 Level3_Customer United_States
Sacramento
Originator: car1.Sacramento1
3701 3582
AS-path translation: { OREGONUNIV UONET }
car1.Sacramento1 (metric 34363)
Origin IGP, metric 0, localpref 100, valid, internal
Community: North_America Lclprf_100 Level3_Customer United_States
Sacramento
Originator: car1.Sacramento1
Best Regards
Reza Motamedi (R.M)
Graduate Research Fellow
Computer and Information Science
University of Oregon
