IPv6 Subnet tool

[Joe Abley]

On 14 Jan 2009, at 09:42, Adam Armstrong wrote:

> Steve Bertrand wrote:
>> Nuno Vieira - nfsi telecom wrote:
>>
>>> err... pasted the wrong sample :-)
>>>
>>> # sipcalc 2001:b18::/48 --v6split=64
>>> -[ipv6 : 2001:b18::/48] - 0
>>>
>>> [Split network]
>>> Network            - 2001:0b18:0000:0000:0000:0000:0000:0000 -
>>>              2001:0b18:0000:0000:ffff:ffff:ffff:ffff
>>> Network            - 2001:0b18:0000:0001:0000:0000:0000:0000 -
>>>              2001:0b18:0000:0001:ffff:ffff:ffff:ffff
>>> Network            - 2001:0b18:0000:0002:0000:0000:0000:0000 -
>>>              2001:0b18:0000:0002:ffff:ffff:ffff:ffff
>>> Network            - 2001:0b18:0000:0003:0000:0000:0000:0000 -
>>>              2001:0b18:0000:0003:ffff:ffff:ffff:ffff
>>> Network            - 2001:0b18:0000:0004:0000:0000:0000:0000 -
>>>              2001:0b18:0000:0004:ffff:ffff:ffff:ffff
>>>
>>
>> Note that it may be prudent to assign up your address space in
>> non-contiguous prefixes.
>>
>> Consider the ramifications of assigning each client a /64 in a
>> sequential fashion, and then having to assign a particular client
>> additional prefixes at a later time.
>>
>> If your network is not flat, then you just broke your ability to
>> aggregate your prefixes from the edge in.
>>
> You would assign them a /56 if they needed more than a /64. If  
> they're the kind of organisation which would have issues with  
> renumbering, you wouldn't have assigned a /64.
>
> A /64 shouldn't really be given to anything but a house, dog kennel  
> or potting shed.

... and if the application really is to assign and route prefixes to  
customers, and not simply to number internal infrastructure within a  
single organisation, it would be a better idea to contact an RIR and  
request a /32 than to worry about how to cut up a /48.

As an aside, I have yet to be convinced that there's any value in  
assigning anything smaller than a /48 to customers, regardless of  
whether they are residential users or giant industrial megaliths.

People whose habit it is to assign /56s seem like they are most likely  
to cause annoyance to customers who are migrating from some other  
provider who gave them (reasonably) a /48.


Joe