BCP: Slicing a /32 for an ISP

Steve Bertrand iaccounts at ibctech.ca
Tue Apr 15 18:06:54 CEST 2008

> Now, I unfortunately have to be a bit nasty again but.... (generally 
> targeting people to maybe wake them up a little bit, hopefully they read 
> this nasty comment before requesting... ;)
> I do hope that you know how large a /32 is and how many customers you 
> could potentially serve with it?

I most certainly do.

> I also hope that you made an actual allocation plan and passed that in 
> when you are going to request or when you requested your prefix from 
> your favorite RIR.

Yes, we did.

> Because, if you 'simply requested a /32' without doing the math, there 
> are a few number of possibilities:

>     - you will never have more than 65k customers


> Just asking though... as it seems a lot of ISP's are 'simply requesting 
> a /32' while they actually don't have a clue on what a /32 is and how 
> little amount of space that actually is.

I requested a /32 based on the fact that this is the base size 
allocation ARIN supplies to ISP's, regardless of size.

There would absolutely have been no way whatsoever I could have even 
remotely justified requesting anything larger than a /32 as the ARIN 
numbering policy stands today or at the time of request.

This has nothing to do with not having a clue regarding the size of a 
/32 is, and what planning was done prior to the request. It has to do 
with following policy, and the ever changing opinions on how to utilize 
the IPv6 space one has.

When an ISP has 50k+ clients, then /32 looks small. When an ISP has 5k 
clients, a /32 looks quite large.

I also know that ARIN has reserved the /29 that encompasses my /32 in 
the event we do magically multiply our size by 'X' fold.

> Thus please people requesting prefixes, make a plan first and don't just 
> do it for the next year. Ask here if wanted, there are a lot of people 
> (also who are not as nasty as me ;) who can help out there in making the 
> right decision.

With our request for IPv6 space, we calculated our utilization that we 
currently have for IPv4, our current client base, and growth trends 
since our inception over 12 years ago. We did not get into too much 
detail on how exactly we were going to number everything.

> Just like a lot of other things: when you have a question: ask the right 
> question and you will receive the right answer. Aka: be verbose.

We did ask questions. I was not on this list at the time of my request. 
I read and still do read and reread the RFC's and countless other 
documentation. This is the first time I've got such detailed and well 
planned out information regarding what other people are doing in regard 
specifically to their address hierarchy.

Aside from that, there are still many, many unanswered questions (such 
as a /64 for PtP or not, whether to use /56's or not etc). I'd 
personally rather wait it out for a little while longer until more 
consensus is made, and go from there.

Regards, and thanks (to all) for the great feedback!


More information about the ipv6-ops mailing list