Comcast route server not reflecting their reality

Tue Sep 10 20:17:12 UTC 2019

On Tue, Sep 10, 2019 at 04:42:10PM +0000, Martijn Schmidt wrote:
> 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

Thanks Martijn,
That's the info I was missing. I have found I can now 65000:XXX or even 65001:XXX to 3356 with the Comcast regional network AS numbers and see the traffic
jump to the 7922 network which has a different set of links to 3356, then I can further do 65001:7922 to get it off 3356 entirely if I need to.

And I can find the specific regional AS# by checking the aforementioned Comcast route views server so it can be applied to only problem areas.

I wish none of this was necessary but when you can't get >100mbit from a Comcast gigabit subscriber into 3356 then customers complain.

-Will