Addressing plan exercise for our IPv6 course

Saku Ytti saku at
Sun Jul 25 09:40:06 CDT 2010

On (2010-07-25 10:28 -0400), Valdis.Kletnieks at and Mark Smith wrote

> >^40)!)%2F((2^40)^1000000+((2^40)-1000000)!)+
> > 
> > So if there are million assigned ULA's there is 36.5% chance of collision, if
> > formula is right.
> Bzzt! Wrong, but thank you for playing.

Point I was trying to convey is that you should not assume ULA to be
globally unique. Visibility of IP can extend past routing, for example
someone could use x-forwarded-for and assume rfc4193 to be as unique as any
other IPv6 address.
I personally have no beef with ULA and I don't mind that it can't be
trusted to be globally unique identifier. It'll still allow well planned
enterprise networks to avoid renumbering in M&A.

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