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Hi Will,</div>
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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<span style="font-family: Calibri, Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255); display: inline !important"> routing
leak which happened a few years ago: <a href="https://dyn.com/blog/widespread-impact-caused-by-level-3-bgp-route-leak/">https://dyn.com/blog/widespread-impact-caused-by-level-3-bgp-route-leak/</a></span></div>
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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</div>
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Best regards,</div>
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Martijn Schmidt</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> NANOG <nanog-bounces@nanog.org> on behalf of Will Orton <will@loopfree.net><br>
<b>Sent:</b> 10 September 2019 01:06<br>
<b>To:</b> nanog@nanog.org <nanog@nanog.org><br>
<b>Subject:</b> Comcast route server not reflecting their reality</font>
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<div class="PlainText">I'm seeing odditiies when trying to traffic-engineering my way around an AS 3356-to-7922 performance issue.<br>
<br>
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.<br>
When I do that, at route-server.newyork.ny.ibone.comcast.net I see the AS-path for my /19 change from:<br>
3356 <me><br>
to:<br>
2914 <me><br>
<br>
which makes sense as I also have transit from 2914.<br>
<br>
So that's great, 7922 should be routing to me via 2914 or, any path not via 3356.<br>
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> !<br>
<br>
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?<br>
<br>
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...<br>
<br>
-Will<br>
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