Using /126 for IPv6 router links

Mark Smith nanog at
Wed Jan 27 04:44:25 UTC 2010

On Tue, 26 Jan 2010 06:38:43 -0800 (PST)
David Barak <thegameiam at> wrote:

> From: Mark Smith nanog at
> >Why can't IPv6 node addressing be as easy to understand and work with
> >as Ethernet addresses? They were designed in the early 1980s*. 28 years
> >or so years later, it's time for layer 3 addressing to catch up.
> Becase Ethernet addresses are only locally significant, are not manually assigned in the vast majority of cases,

That makes them globally significant - and that's what makes them
'plug-and-play'. Ethernet addresses are bigger than they operationally
need to be, and the 'plug-and-play' nature of them is what we got for
that price.

That being said, my comment is not specifically about how Ethernet
addressing works, it is about how easy Ethernet addressing is to use.
It was a rhetorical question.

I think it'd be a tragedy if IPv6 addressing is harder to work with
than than Ethernet, Appletalk, IPX and a number of other protocols
designed at least 10 years or more before it. I really don't understand
why people seem so keen on making IPv6 addressing's model look like
IPv4's when the primary reason for IPv4's addressing models was the
severe lack of address space. 

btw, did you read the paper I linked too?

> and changing a MAC by replacing a NIC has no bearing on the
> configuration of a { server | router ACL | etc }.
> Layer 3 addressing is globally significant, and the case we're discussing is addresses which are human-assigned rather than automatically configured.  Link-local autoconfiguration in IPv6 works like a champ, and behaves pretty much the way I would want it to.  Global addressing approaches, on the other hand, are highly optimized in directions which make them less flexible or have surprising consequences (hence this thread).
> David Barak
> Need Geek Rock? Try The Franchise: 

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