/127 between routers?

[sthaug at nethelp.no]

> I could assign /64s per ptp without difficulty. Should I also assign
> /64s per loopback? Should I really being using some form of EUI-64 for
> these addresses, to guarantee the interface ID is unique no matter
> what the network prefix? What happens when I replace hardware and
> EUI-64 changes ptp/loopback addresses?

You certainly *don't* want your (globally routable) link addresses to
change just because you replace hardware (e.g. you install a card with
a new MAC address). You *will* get a new link local address, but that's
okay as long as the global address doesn't change.

The obvious conclusion is that the global address should be independent 
of any interface MAC address. It is, of course, possible to create such
addresses which are still in the modified EUI-64 format - I just don't
see any point in doing so when a nice /112, /126 or similar works equally
well.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no