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
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’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
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.
participants (2)
-
Hamish McGlinn -
Reza Motamedi