I've been involved in IX renumbering efforts because exchange(s)
decided to use /25's instead of /24's.    It's painful because
troubleshooting can be a little difficult as differing subnetmasks are
in play.   If you have the address space, use a /24.    ARIN has IPv4
address space specifically reserved for the use by IXPs.

charles

On Sat, Apr 4, 2015 at 8:35 PM, Mike Hammett <na...@ics-il.net> wrote:
> Okay, so I decided to look at what current IXes are doing.
>
> It looks like AMS-IX, Equinix and Coresite as well as some of the smaller 
> IXes are all using /64s for their IX fabrics. Seems to be a slam dunk then as 
> how to handle the IPv6. We've got a /48, so a /64 per IX. For all of those 
> advocating otherwise, do you have much experience with IXes? Multiple people 
> talked about routing. There is no routing within an IX. I may grow, but an IX 
> in a tier-2 American city will never scale larger than AMS-IX. If it's good 
> enough for them, it's good enough for me.
>
> Back to v4, I went through a few pages of PeeringDB and most everyone used a 
> /24 or larger. INEX appears to use a /25 for each of their segments. IX 
> Australia uses mainly /24s, but two locations split a /24 into /25s. A couple 
> of the smaller single location US IXes used /25s and /26s. It seems there's 
> precedent for people using smaller than /24s, but it's not overly common. 
> Cash and address space preservation. What does the community think about IXes 
> on smaller than /24s?
>
>
>
>
>
>
> -----
> Mike Hammett
> Intelligent Computing Solutions
> http://www.ics-il.com
>
>
>
> ----- Original Message -----
>
> From: "Brendan Halley" <bren...@halley.net.au>
> To: "Mike Hammett" <na...@ics-il.net>
> Cc: nanog@nanog.org
> Sent: Saturday, April 4, 2015 6:10:34 PM
> Subject: Re: Small IX IP Blocks
>
>
> IPv4 and IPv6 subnets are different. While a single IPv4 is taken to be a 
> single device, an IPv6 /64 is designed to be treated as an end user subnet.
> https://tools.ietf.org/html/rfc3177 section 3.
> On 05/04/2015 9:05 am, "Mike Hammett" < na...@ics-il.net > wrote:
>
>
> That makes sense. I do recall now reading about having that 8 bit separation 
> between tiers of networks. However, in an IX everyone is supposed to be able 
> to talk to everyone else. Traditionally (AFAIK), it's all been on the same 
> subnet. At least the ones I've been involved with have been single subnets, 
> but that's v4 too.
>
>
>
>
> -----
> Mike Hammett
> Intelligent Computing Solutions
> http://www.ics-il.com
>
>
>
> ----- Original Message -----
>
> From: "Valdis Kletnieks" < valdis.kletni...@vt.edu >
> To: "Mike Hammett" < na...@ics-il.net >
> Cc: "NANOG" < nanog@nanog.org >
> Sent: Saturday, April 4, 2015 5:49:37 PM
> Subject: Re: Small IX IP Blocks
>
> On Sat, 04 Apr 2015 16:06:02 -0500, Mike Hammett said:
>
>> I am starting up a small IX. The thought process was a /24 for every IX
>> location (there will be multiple of them geographically disparate), even 
>> though
>> we nqever expected anywhere near that many on a given fabric. Then okay, how 
>> do
> < we d o v6? We got a /48, so the thought was a /64 for each.
>
> You probably want a /56 for each so you can hand a /64 to each customner.
>
> That way, customer isolation becomes easy because it's a routing problem.
> If customers share a subnet, it gets a little harder....
>
>
>
>

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