[arin-ppml] V6 address allocation policy
mysidia at gmail.com
Sun Jan 17 22:07:55 EST 2010
On Sun, Jan 17, 2010 at 8:27 PM, Owen DeLong <owen at delong.com> wrote:
> On Jan 17, 2010, at 7:46 AM, William Herrin wrote:
>> On Sat, Jan 16, 2010 at 7:55 PM, Owen DeLong <owen at delong.com> wrote:
>> Practically speaking, we should start to see anecdotes about ULA
>> collisions as folks try to connect 100 to 1000 organizations together,
>> still a usefully large number but far fewer than RFC 4193 implies.
> Practically speaking, even if you buy into that argument, you're still
> quite a bit better off than RFC-1918.
If you have a V6 ULA collision, you may be a lot worse off than you
were with a IPv4 RFC-1918 collision.
The thing is: you can probably mitigate an RFC-1918 collision (when
merging companies, for example), by using creative NAT rewriting
rules; NAT'ing both sources and destinations, to provide connectivity
for the transition period, when the merging companies renumber to
In the IPv6 world, so far, there is no such thing as NAT.
You cannot use NAT or translation to mitigate an address space
collision, when the tool and even the specification has not been
A RFC-1918 collision can be much less of an issue than a ULA
collision, even though it is more likely.
So the combination of IPv6 + ULA can make you a lot worse off in some
When the specifications for IPv6 NAT come out, and vendors start
making equipment that can NAT map a block of V6 addresses 1:1 into
another block of addresses, _then_ we can consider you a lot better
off with ULA in that scenario.
> So, in order for ULA to buy you nothing, you'd have to be able to argue
> that 1:3 and 1:1,048,576 are equivalent risks. If you are willing to make
> bets like that, I want to be your bookie.
> Even if this is true (I'm not completely convinced), you're comparing
> ULA at 1:100<n<1000 vs. RFC-1918 at 1:0.003.
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