Cogent IPv6

sthaug at sthaug at
Thu Jun 9 12:26:23 UTC 2011

> > Of course, just because you allocate a /112 (or shorter) in your
> > database doesn't mean you have to use it.  You could also allocate a
> > /112 for a point-to-point link and use a /127 (e.g. addresses ::a and
> > ::b).
> Please don't use /127:
> Use of /127 Prefix Length Between Routers Considered Harmful

Please *do* consider using /127 on "real" point-to-point links (e.g.
SDH/SONET, serial) - especially if you have internet facing links and
are using a hardware based forwarding platform from vendors like Cisco
or Juniper.

This may be your simplest choice if you want to avoid the "ping-pong"
problem which is very real (on some platforms). See

Steinar Haug, Nethelp consulting, sthaug at

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