Current Consensus on IPv6 Customer Allocation Size

Tim Densmore tdensmore at
Wed Aug 1 23:03:03 CEST 2012

Hi Chris,

Thanks for the link!  I had actually read through it recently and found 
it quite useful.  I find the back and forth between /64 vs /12[67] on 
P2P links interesting.

I've read rfc 3177, and though some of it was above my head, I couldn't 
really find anything in it that really defined *why* a /48 was preferred 
(GSE, 6to4, and Site Local require /48, so /48 is best was what I took 
away).  As far as I can tell, the layman arguments in favor go like this:

- /48 is likely to be equal to /24 (v4) bgp-wise, and anything longer is 
likely to be filtered.

- /48 for *everyone* allows for uniform customer allocation size.

- It's "easy" to forsee that someday in the future people will need more 
than 256 subnets in the home, and since nibble boundaries are considered 
a must, then /48 is the only option.

Is that about right?

I think I'd have a hard time pitching extra cash outlay for a /28.

Thanks again!


On 8/1/2012 1:49 PM, Chris Grundemann wrote:
> Best Current Operational Practice (BCOP) on IPv6 Subnetting:
> /48 per site is best. I would highly recommend swallowing the ~$2k/yr
> and get the allocation you need now, so that your network can grow in
> a structured, homogenous manner. Rather than fighting fires later to
> save a buck now (I mean, I have to guess that buying even one router a
> year blows that cost out of the water anyway - even a line card...).
> Cheers,
> ~Chris

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