[ipv6-wg] /127 for point to point links

Vegard,

> Hello. We've stumbled across a problem with a router manufacturer, which
> won't implement support for /127 prefix lengths. Now, we do have
> peering/transit partners using /127 on their p2p links. The result is
> that we either cannot peer with them, or will have to get new routers.
> 
> RFC 3627 states that /127 is considered harmful, however I do feel this
> RFC confuse people since it doesn't propose a definite solution. It
> suggests a number of solutions and indicates using /64 is the right
> thing. I must say I strongly disagree on that conclusion. Wasting so
> much address space on point to point links just makes no sense to me.
> 
> So I'm not sure what to do here. I have to convince someone; either our
> partners or the router manufacturer. I have the impression that /127 is
> used widely out there.

let's be clear that you are not wasting address space by using a /64 on a point to point link. IPv6 address space is as close to an infinite resource when it comes to the number of /64s.
a point to point link uses 2 addresses out of 2^64 a random multi-access link doesn't use a significantly larger proportion in any case.

the argument for using /127 is for example that there is no confusion what the address on the other end is. or that you will have no problem with looping to unassigned addresses within the prefix.

if you have an implementation which doesn't support /127 you can just use a /128 on each end.

cheers,
Ole