Re: What can I infer from show ip route and similar BGP commands?
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 motam...@cs.uoregon.edu
wrote:
Hello NANOG,
I’m a researcher and I was trying to understand the data I collected from
some BGP Looking Glasses. Basically, I was hoping to see if BGP records can
tell me where my university’s provider (AS3701) is peering with its
providers. I issued two BGP queries to Level3’s LGs, one in Seattle and one
in Amsterdam for my school’s 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 “car1.Sacramento1” 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 “Internal/External” keywords 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
What can I infer from show ip route and similar BGP commands?
Hello NANOG,
I’m a researcher and I was trying to understand the data I collected from
some BGP Looking Glasses. Basically, I was hoping to see if BGP records can
tell me where my university’s provider (AS3701) is peering with its
providers. I issued two BGP queries to Level3’s LGs, one in Seattle and one
in Amsterdam for my school’s 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 “car1.Sacramento1” 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 “Internal/External” keywords 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
Re: What can I infer from show ip route and similar BGP commands?
Thanks Joel for your detailed explanation. It was very informative. I have been using routeviews for sometime, but given that I could get this amount of information from other sources, I decided to give this a try. On another note, do you think there is any value in checking the next hop IP? I have been checking and it looks as if when the IP is in the AS at the head of the AS path, the entry is associated with an iBGP record, right? I just used the ripe stat to map IPs to AS and it always holds when there is an AS for the next hop IP. Thanks again for your input.
