Using /126 for IPv6 router links

Mark Andrews marka at
Wed Jan 27 13:26:34 UTC 2010

In message <m2sk9rsobb.wl%randy at>, Randy Bush writes:
> >>> the general intent of a class B allocation is that it is large enough
> >>> for nearly everybody, with nearly everybody including all but the
> >>> largest of organisations.
> >> That would, indeed, work if we weren't short of class B networks
> >> to assign.
> > Would you clarify? Seriously?
> we used to think we were not short of class B networks

Really?  Do you have a citation?  It should have been clear to
anyone that thought about it that IPv4 address where not big enough
to support every man and his dog having a network.

I know when I was getting my first class B address block in '88
that it was obviously not sustainable but I'll get one while I can
because that and class C's were all that were available and it could
be justified under the rules as they stood then.

CIDR when it came along didn't change my opinion, though it did
delay the inevitable as did PNAT.

I don't see the same thing with /48 as the basic allocation provided
RIR's don't do greenfield all the time but instead re-allocate
blocks when they are not maintained.  Always doing greenfield
allocations will exhaust any allocation scheme in time.


Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

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