Using /126 for IPv6 router links

Mark Smith nanog at 85d5b20a518b8f6864949bd940457dc124746ddc.nosense.org
Mon Jan 25 22:06:57 CST 2010


On Mon, 25 Jan 2010 15:15:55 -0500
"TJ" <trejrco at gmail.com> wrote:

> > -----Original Message-----
> > From: Tim Durack [mailto:tdurack at gmail.com]
> > Sent: Monday, January 25, 2010 14:03
> > To: TJ
> > Cc: nanog at nanog.org
> > Subject: Re: Using /126 for IPv6 router links
> 
> <<snip>>
> 
> > 
> > 2^128 is a "very big number." However, from a network engineering
> > perspective, IPv6 is really only 64bits of network address space. 2^64
> > is still a "very big number."
> > 
> > An end-user assignment /48 is really only 2^16 networks. That's not
> > very big once you start planning a human-friendly repeatable number
> > plan.
> > 
> > An ISP allocation is /32, which is only 2^16 /48s. Again, not that big.
> > 
> > Once you start planning a practical address plan, IPv6 isn't as big as
> > everybody keeps saying...
> 
> 
> I didn't realize "human friendly" was even a nominal design consideration,
> especially as different humans have different tolerances for defining
> "friendly"  :)
> 

This from people who can probably do decimal to binary conversion
and back again for IPv4 subnetting in their head and are proud of
it. Surely IPv6 hex to binary and back again can be the new party
trick? :-)



> I (continue to) maintain that:
> *) 2^16 is still a pretty good size number, even allowing for aggregation /
> summarization.
> *) If you are large enough that this isn't true - you should (have)
> request(ed) more, naturally - each bit doubles your space ...
> 
> 
> 
> /TJ
> 
> 
> 




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