Re: What flexibility do 6to4 NAT have with address formats?

[Brian E Carpenter <brian.e.carpenter at gmail.com>]

On 2009-10-14 14:09, Christian Huitema wrote:
>>> The second question regards the uniqueness of host
>>> identifiers. Suppose we define the address used for stateless
>>> translation as: 32 bit "provider" prefix, 32 bit IPv4
>>> address, and a constant identifier, either 0 or the "checksum
>>> neutrality" value, which is only a function of the provider
>>> prefix. Suppose now that for some reason there are two "IPv4
>>> addressed" hosts on the same link, e.g. because many servers
>>> are located in the same server room. The two hosts will have
>>> different addresses, in different 64 bit subnets, but they
>>> will also have different host identifiers. Is that OK?
>> Why wouldn't it be OK? I can't see why it's a question.
>> The normal expectation is that different hosts have different
>> IIDs so I am curious why this matters.
> 
> I just realize I made "typo". I meant to say " The two hosts will have
> different addresses, in different 64 bit subnets, but they will also have 
> the same host identifiers. Is that OK?

Well, that would be OK if you set U=0 as far as I can see.
It might be an odd situation, but then nobody should ever rely on
their uniqueness. It might be safer to make U=0 mandatory
for these synthetic addresses in all cases.

If you don't respect the UG bits we are asking for trouble anyway.

   Brian