Small IX IP Blocks

Mike Hammett nanog at
Sun Apr 5 00:35:55 UTC 2015

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 

----- Original Message -----

From: "Brendan Halley" <brendan at> 
To: "Mike Hammett" <nanog at> 
Cc: nanog at 
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. section 3. 
On 05/04/2015 9:05 am, "Mike Hammett" < nanog at > 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 

----- Original Message ----- 

From: "Valdis Kletnieks" < Valdis.Kletnieks at > 
To: "Mike Hammett" < nanog at > 
Cc: "NANOG" < nanog at > 
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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