On 27 Mar 2015 9:13 am, "Sanjeev Gupta" <ghane0@gmail.com> wrote:
>> Technically, I think you mean NPTv6, as per RFC 6296.
>> It’s disappointing but not unexpected that sites are doing this.
>> The homenet approach is that hosts are multi-addressed with ULA and globals. They use ULAs internally, which provides a decent level of renumbering protection, and globals externally.
>> Having a single IP address is IPv4 thinking.
>
> Tim, thank you for the reference, we are using something close-to-but-not RFC6296.

That's not a recommended deployment strategy. A much better strategy is the one recommended by RFC 7368.

Bear in mind that RFC 6296 is classified as experimental, and to my knowledge is not used by any other ISP in this way. IIRC it was originally rushed through the prices due to a very unique situation in Japan, and even there it is used to convert between two different global prefixes, not ULA.

Using NPTv6 will break applications, such as video chat clients, which are built on the assumption that IPv6 does not use NAT and thus in IPv6 implement only firewall traversal but not NAT traversal. That assumption is true in the vast majority of IPv6 deployments, so those apps may never support this more of operation.

Also - if you're using ULAs, be aware that ULAs are specified to be globally unique, i.e. all the ULA prefixes used in your network should be different from all the ULA prefixes used elsewhere in the world. ULA achieves this by requiring that ULA prefixes be generated randomly to avoid collisions. If you're not doing this, you may encounter other forms of breakage.

"It works like this in IPv4" doesn't means it will work in IPv6. In IPv4, virtually everybody uses NAT. In IPv6, virtually nobody does.

Why can't you provide global IPv6 addresses? Most IPv6 deployments have to deal with IPv6 prefix changes, and none that I'm aware of have chosen to use ULA as a result.