[176687] in North American Network Operators' Group
Re: What can I infer from "show ip route" and similar BGP commands?
daemon@ATHENA.MIT.EDU (Hamish McGlinn)
Tue Dec 9 18:40:26 2014
X-Original-To: nanog@nanog.org
In-Reply-To: <CACGuEhF5nfvZ_Cov_mnVARKu6Lngdf9ajHXDHbqnynNAP-v21w@mail.gmail.com>
Date: Tue, 9 Dec 2014 17:12:04 +1300
From: Hamish McGlinn <hmcglinn@gmail.com>
To: Reza Motamedi <motamedi@cs.uoregon.edu>
Cc: nanog@nanog.org
Errors-To: nanog-bounces@nanog.org
Hi there,
Perhaps this would be easier and help you out:
http://bgp.he.net/AS3701#_graph4
Cheers,
Hamish
On Tue, Dec 9, 2014 at 12:48 PM, Reza Motamedi <motamedi@cs.uoregon.edu>
wrote:
> Hello NANOG,
>
> I=E2=80=99m a researcher and I was trying to understand the data I collec=
ted from
> some BGP Looking Glasses. Basically, I was hoping to see if BGP records c=
an
> tell me where my university=E2=80=99s provider (AS3701) is peering with i=
ts
> providers. I issued two BGP queries to Level3=E2=80=99s LGs, one in Seatt=
le and one
> in Amsterdam for my school=E2=80=99s prefix. My strong guess was that our=
provider
> (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 key=
words in the data.
> My main issue is that the keywords are not always available. In some othe=
r
> 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 somebo=
dy
> 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 Seatt=
le
> 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
>
