Cogent - Google - HE Fun

Matthew D. Hardeman mhardeman at
Thu Mar 10 22:19:23 UTC 2016

I have contemplated whether such mechanisms matter to Cogent, etc.

I’m inclined to think that if Google is willing to pull the routes and they still don’t blink, then certainly us smaller shops aren’t going to impact them…

However…  If enough prefixes disappear from the _apparent_ Cogent table as viewed by outsiders, this may ultimately impact their sales of new interconnection….

For those of us multihomed with Cogent and other transit providers on IPv6 there is a less drastic way to impact the perceived value of Cogent’s IPv6 routing table to outsiders and especially to Cogent’s peers — and one that still doesn’t negatively impact the single-home customers of Cogent:

"set community 174:3000" on your IPv6 advertisement to Cogent.  This will constrain the advertisement to Cogent and Cogent’s customers only.  For good measure, prepend your own AS to this advertisement at least a couple of times, potentially discouraging even Cogent customers who see the route from using it if they have other transit.  It will prevent the path via Cogent being selected by Cogent IPv6 peers versus your other transit providers.

> On Mar 10, 2016, at 3:47 PM, Fredy Kuenzler <kuenzler at> wrote:
> Am 10.03.2016 um 22:25 schrieb Damien Burke <damien at>:
>> Anyone who is multihomed with cogent ipv6 in their mix should shutdown their IPv6 bgp session. Let’s see if we can make their graph freefall.
> Alternative:
> set community [do not announce to Cogent]
> *SCNR*

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