Strange entries from AS1 in global table

Anurag Bhatia me at anuragbhatia.com
Sun Aug 4 05:15:57 UTC 2013


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

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