Level 3 currently uses AS 1 in their MPLS network. I'm unsure if it's used elsewhere, but AS 1 could get into the AS paths of prefixes in the global routing table this way. I wouldn't expect to see it originating routes outside of the WAN interface for customers though and those are typically way too small to make it into the global routing table.
-Vinny -----Original Message----- From: Humberto Galiza [mailto:humbertogal...@gmail.com] Sent: Thursday, August 08, 2013 6:25 AM To: Anurag Bhatia Cc: NANOG Mailing List Subject: Re: Strange entries from AS1 in global table 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 <m...@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
