Re: [v6ops] ULA precedence [Thoughts about wider operational input]

[Brian E Carpenter <[e-mail]>]

On 06-May-22 15:23, Michael Richardson wrote:
> 
>      fred> You might look at section 3 of RFC 4193, and specifically at 
the global ID
>      fred> mentioned in section 3.2. I'm looking at the first 48 bits of the address
>      fred> and calling it a routing prefix. Let me put the question back to you:
>      fred> starting from RFC 4193, what other prefix would be under consideration, and
>      fred> why would it be under consideration?
> 
> Ed Horley <[e-mail]> wrote:
>      > Yes, I am familiar with section 3.2 - my question is because several on
>      > this mailing list in the past have said to ignore the stated pseudo-random
>      > requirement in that section and not to follow this section which 
states
>      > "Specifically, these prefixes are not designed to aggregate." Obviously, if
>      > you don't follow that then the question comes back to are we still assuming
>      > a /48? Or do we mean something different when we say "same prefix"? Is that
>      > defaulting to just the overall ULA prefix itself because people are
>      > designing networks starting at fd01::/32, fd02::/32, fd03::/32...
>      > fdff::/32, etc. which I completely understand is not how 4193 says to do
>      > it, but it is happening, so we need to be thinking about it perhaps? Just
>      > curious if anyone else is seeing this behavior with their customers at
>      > all?
> 
> I'm understanding the question to be:
> 
> For instance, if two enterprises with internal ULA-R's merged, then they
> might prefer that ULA1 was used as a source address even when speaking to
> ULA2, rather than a GUA.
> 
> (Should they renumber into a single ULA?  Probably, but this is a place 
where
> IPv6 and ULAs are supposed to be a win)
> 
> If I have fd01:abcd:1234:4567::A/64 as an address, one can see how a system
> could be automatically configured to prefer that address when talking to
> destinations like fd01:abcd:1234::/48 ("ULA1")
> 
> I don't know how it would know to use fd01:abcd:1234:4567::A/64 when talking
> to fd02:fedc:8765::/48 ("ULA2").  Really, this comes back to the general
> source address selection problem with multi-homing, which homenet tried 
to solve.

Surely, two addresses in fd00::/8 will always have a longer match than
either for them does with any address in 2000::/3 ?

That being so, section 10.6 of RFC6724 will still work, won't it?

    Brian

> 
> --
> Michael Richardson <[e-mail]>   . o O ( IPv6 IøT consulting )
>             Sandelman Software Works Inc, Ottawa and Worldwide
> 
> 
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