Strange entries from AS1 in global table

Brad Fleming bdflemin at gmail.com
Thu Aug 8 14:48:46 UTC 2013


I think Level(3) uses it for at least some L3 MPLS VPN stuff. We peer with that AS for dedicated SIP service transport for example.


On Aug 8, 2013, at 5:25 AM, Humberto Galiza <humbertogaliza at gmail.com> wrote:

> Looking at our routers I can see this:
> 3549 3356 26114 1 i
> 12956 1239 23520 23383 1 ?
> 
> but neither 26114 or 23383 are Brazilian ISP´s. Anyway, I guess it´s
> probably leaked routes or even use of AS 1 as private one (I don´t
> think level3 guys are using this AS anymore...).
> 
> Cheers,
> Humberto Galiza
> 
> 
> 2013/8/4 Anurag Bhatia <me at anuragbhatia.com>:
>> Hello everyone
>> 
>> 
>> I was looking at global IPv4 table and saw some strange entries from AS1.
>> As per ARIN whois AS1 seems to be with Level3 but I noticed few prefixes of
>> Brazil based ISP - Netvip
>> 
>> 
>> http://bgp.he.net/AS1#_prefixes
>> 
>> 
>> 
>> Looking at any prefix in detail, it seems like there are multiple ASNs
>> announcing same prefix.
>> 
>> E.g 177.185.96.0/24 - is being announced by AS1 as well as AS52931
>> (Netvip's allocated ASN). Same is true with 177.185.98.0/24,
>> 177.185.98.0/24and so on.
>> http://bgp.he.net/net/177.185.96.0/24
>> 
>> So seems like AS1 acting like a mirror for all announcements of AS52931. To
>> see who exactly gave "transit" to AS1 by Netvip in Brazil, I checked Oregon
>> and noticed these routes:
>> 
>> 3356 3549 16735 52931 1 i
>> 
>> 
>> 
>> Seems like AS52931 itself is acting as transit for AS1 (and AS16735 which
>> seems like a backbone ISP in Brazil) is not filtering these routes further
>> passing to Level3 (AS3549+AS3356).
>> 
>> 
>> 
>> I am curious to know what could be possible reason for an ASN like AS1
>> acting in exact mirror of AS52931? Could it be a case of internal use of
>> AS1 (assuming it to be private ASN)? May be it's a case of leaked internal
>> routes?
>> 
>> 
>> 
>> Appreciate your time & answer.
>> 
>> 
>> 
>> Thanks.
>> 
>> --
>> 
>> Anurag Bhatia
>> anuragbhatia.com
>> 
>> Linkedin <http://in.linkedin.com/in/anuragbhatia21> |
>> Twitter<https://twitter.com/anurag_bhatia>
>> Skype: anuragbhatia.com
> 




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