Cogent IPv6

Kelly Setzer Kelly.Setzer at
Thu Jun 9 01:58:18 UTC 2011

> -----Original Message-----
> From: ryan at [mailto:ryan at]
> Sent: Wednesday, June 08, 2011 9:19 AM
> To: nanog at
> Subject: Re: Cogent IPv6
> On Wed, 8 Jun 2011 09:51:21 -0400, Nick Olsen wrote:
> > I'm sure someone here is doing IPv6 peering with cogent. We've got a
> > Gig
> We have separate v4 and v6 sessions with them on the same dual-stack
> interface (a v4 /29 and v6 /112 on the interface).  One session is
> between our v4 address and theirs, and carries v4 prefixes only.  Then
> another session between v6 addresses that carries v6 prefixes only.

IPv6 newbie alert!

I thought the maximum prefix length for IPv6 was 64 bits, so the comment about a v6 /112 for peering vexed me.  I have Googled so much that Larry Page called me and asked me to stop.

Can someone please point me to a resource that explains how IPv6 subnets larger than 64 bits function and how they would typically be used?


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