IPv6 Addressing Help

Nathan Ward nanog at daork.net
Wed Aug 19 16:36:12 CDT 2009

On 16/08/2009, at 1:29 AM, William Herrin wrote:

> Start with: /32
> Sparsely allocate 200 /56's
> Total remaining space: in excess of /33. In fact, you haven't consumed
> a single /48.
> Expandability by altering the netmask: to /40
> Largest allocation still possible: only /40

My suggestion was to sparsely allocate /48s to push addresses to POPs  
(or something topologically relevant to your network, maybe even  
NASes) as required.

So, 200 /56s, sparsely allocated, would still be one /48 (or however  
many /48s you want to have around your network, as above).

Sparse allocation within each of those /48s is also potentially a good  
idea - case by case. Doesn't make sense on an ADSL pool where everyone  
has the same length. Makes sense where you're assigning address space  
to customers who are likely to have different prefix lengths.

Sparse allocation of /48s within a /32 has the advantage of letting  
you grow each area of your address space in each area independently.  
You can put one /48 in one POP or NAS or something, and 10 in another,  
without having to break any of your addressing architecture rules.

/48s seem flexible enough to me, but perhaps you want to use this  
technique with /44s or /40s, or something.

Nathan Ward

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