Using /126 for IPv6 router links

Leo Bicknell bicknell at
Sun Jan 24 04:28:21 UTC 2010

In a message written on Sat, Jan 23, 2010 at 01:52:21PM +0100, Mathias Seiler wrote:
> I use a /126 if possible but have also configured one /64 just for the link between two routers. This works great but when I think that I'm wasting 2^64 - 2 addresses here it feels plain wrong.
> So what do you think? Good? Bad? Ugly? /127 ? ;)

I have used /126's, /127's, and others, based on peers preference.

I personally have a fondness for /112's, as it gives you more than
2 addresses, and a DNS bit boundary.

For all the pontification about how there are enough /64's to number
all the grains of sand, or other nonsense, I think that ignores too
much operational information.

rDNS is important, and becomes harder in IPv6.  Making it easier
is importnat.

Having a scan of a /64 fill your P2P T1 is poor design, all because
you assigned 2^64 addresses to a link that will never have more
than 2 functional devices.

Most importantly, we should not let any vendor code any of these
into software or silicon, in case we need to change later.

       Leo Bicknell - bicknell at - CCIE 3440
        PGP keys at
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