Hi Will, Unlike AS2914 which purely interconnects with AS7922, it seems that AS3356 also has direct interconnections to the various Comcast subsidiary networks which are hidden from the DFZ through no-export communities.. I figured this out due to a routing leak which happened a few years ago: https://dyn.com/blog/widespread-impact-caused-by-level-3-bgp-route-leak/
Give it a shot with the following list of communities - that should swing your traffic away from the AS3356 links: 65000:7922 65000:7015 65000:7016 65000:7725 65000:13367 65000:20214 65000:22909 65000:33287 65000:33490 65000:33491 65000:33650 65000:33651 65000:33652 65000:33657 65000:33659 65000:33660 65000:33662 65000:33667 65000:33668 Best regards, Martijn Schmidt ________________________________ From: NANOG <nanog-boun...@nanog.org> on behalf of Will Orton <w...@loopfree.net> Sent: 10 September 2019 01:06 To: nanog@nanog.org <nanog@nanog.org> Subject: Comcast route server not reflecting their reality I'm seeing odditiies when trying to traffic-engineering my way around an AS 3356-to-7922 performance issue. I buy transit from 3356 and announce my /19 to 3356. I set traffic engineering community 65000:7922 to supress announcement of it from 3356 to 7922. When I do that, at route-server.newyork.ny.ibone.comcast.net I see the AS-path for my /19 change from: 3356 <me> to: 2914 <me> which makes sense as I also have transit from 2914. So that's great, 7922 should be routing to me via 2914 or, any path not via 3356. But then if I go to a customer location on 7922's network, and traceroute to my /19, it still goes via 7922 3356 <me> ! Is 7922's looking glass no longer reflecting actual route selection in their network? Does Comcast do traffic engineering that is not otherwise reflected at their looking glass? If I deaggregate my /19 and announce a /24 from it to 2914, I can draw the inbound traffic to me away from the 7922 3356 path. Which is not a real nice long-term solution... -Will
