Link local for P-t-P links? (Was: IPv6 prefixes longer then /64: are they possible in DOCSIS networks?)

Ray Soucy rps at
Thu Dec 1 02:52:30 UTC 2011

I was half joking, but you know, you might be on to something there.

I'll have to try it out and see what the implications are.

I know that for our gear, it uses the interface address so we can map
rDNS to something useful.  The other thing to look into would be
neighbor configuration for routing protocols, using a routable address
does tend to make things a bit cleaner, but maybe those are worth
giving up.

The other option, of course, is to just use longer prefixes (e.g.
126), but just using Link-Local would save some effort in allocation
of IPv6 networks for links between routers.

I'd love to see someone like Randy Bush weigh in on it (poke poke, I
know you're reading).

The use of global IPv6 for link networks is something I never really questioned.

On Wed, Nov 30, 2011 at 9:40 PM, Mike Jones <mike at> wrote:
> On 1 December 2011 02:22, Ray Soucy <rps at> wrote:
>> I for one get really irritated when my traceroutes and pings are
>> broken and I need to troubleshoot things. ;-)  But I guess something
>> has to give.
> My home connection gets IPv6 connectivity via a tunnelbroker tunnel, i
> didn't use the "tunnel interface" addresses in the instructions but
> configured it without addresses, traceroutes (in all directions) show
> up with the routers single assigned global address.
> Routers would still have a single global address assigned to loopback
> (or anywhere) for management/packet generation purposes so traceroutes
> should work fine, although rather than getting a per-interface address
> you'll get a per-router address. What addresses do you currently get
> in the real world? some routers give a loopback address, some give the
> ingress interface, some give the egress interface, all you can safely
> assume from the address is the router it hit.
> - Mike

Ray Soucy

Epic Communications Specialist

Phone: +1 (207) 561-3526

Networkmaine, a Unit of the University of Maine System

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