Private use of non-RFC1918 IP space

Nathan Ward nanog at
Tue Feb 3 23:43:21 UTC 2009

On 4/02/2009, at 12:25 PM, Owen DeLong wrote:

> There is the ULA-Random space, but, I'm not sure if that got  
> ratified or was
> rescinded.  I really don't see a need for RFC-1918 in
> the IPv6 world.  RFC-1918 was intended to solve a problem with a  
> shortage
> of address space by allowing disparate private networks to recycle  
> the same
> numbers behind NAT or for use on non-connected networks.  There is no
> such shortage in IPv6. I think it is wiser to number non-connected  
> IPv6 networks
> from valid unique addresses since there is no shortage.

ULA is useful for organisations that cannot get an RIR allocation/ 
assignment, so are likely to need to re-number.

If they number on ULA *in addition to* whatever space their ISP gives  
them, they do not need to alter any internal DNS, ACLs, etc. etc. if/ 
when they re-number. An easy example of a good use for ULA might be  
the internal recursive DNS server addresses that the DHCPv6 server  
hands out.

If they are so inclined, they might even re-number dynamically if they  
get their prefix using PD.

Nathan Ward

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