Current Consensus on IPv6 Customer Allocation Size

Chris Grundemann cgrundemann at
Wed Aug 1 21:49:16 CEST 2012

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...).


On Wed, Aug 1, 2012 at 1:17 PM, Tim Densmore
<tdensmore at> wrote:
> Hi Folks,
> I have read through multiple threads regarding this issue (though most of
> them are years old), and know it may be a can of worms, but I need some
> insight into what people are actually doing in 2012. ARIN "suggests" a /48
> for all customers or sites as far as I can tell, though apparently in the
> past they also had language including /56 assignments in some docs.  I'm
> trying to come up with a reasonable numbering plan that can accommodate /48
> customer assignments from our /32.
> Basically, here's how I'm looking at things in a nutshell.  We currently
> have 8 POPs that need subnets allocated, but obviously I want to leave room
> for future growth.  This leaves me with /36 or /37 per-POP (yes, I know that
> the idea of /37 might bother some folks) which would allow me 16 or 32 POPs
> respectively.  Some POPs are obviously smaller than others, but I don't want
> to get into variable sized allocations per-POP.  Even with a /36 per-POP,
> when using /48, this allows me a maximum of 4096 allocations before having
> to add a second /36 to the same POP.  This is fine for business connections,
> but kind of dicey for residential services. Obviously we could go back to
> ARIN for another allocation if we end up in a bind down the road, but there
> is a real cost associated with changing designation from a "small" to
> "large" org (we actually qualify as a medium org, but nibble boundary
> allocations) that I'd prefer to avoid.
> Is the current (again, 2012 - most threads and books that I have read are al
> least a few years old) consensus that a /48 per-residential-user really
> justified?  Opinions or pointers to current Fine Manuals to read would be
> most appreciated.
> Thanks,
> TD


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