Re: DHCPv6 PD & Routing Questions

[Owen DeLong <owen () delong com>]

> On 2015-11-20 15:36, Owen DeLong wrote:
> > > On Nov 20, 2015, at 13:35 , Jim Burwell <jimb () jsbc cc> wrote:
> > >
> > > Hi,
> > >
> > > Have a simple couple of questions here. 
> > >
> > > In my admittedly cursory glances over the DHCPv6 RFCs, I don't see any
> > > reference to the protocol having any role in managing the routing of
> > > prefixes it delegates.  Perhaps I missed it, but I somewhat expected the
> > > omission of this responsibility would be the case.
> > >
> > > My questions are:
> > >
> > > 1) Does the DHCPv6 protocol include any standards/mechanisms/methods for
> > > managing routes to prefixes it delegates, or does it consider this
> > > outside of its function?  (I suspect the latter)
> > Yes and no…
> >
> > DHCPv6 doesn’t include anything specifically per se, but it does require that
> > the local router sees the DHCPv6 PD answer in the process of passing it
> > along to the target, and there’s a pretty obvious expectation that said router
> > will have to arrange to do the needful in that respect.
> >
> > > 2) What are the most common ways of managing the routing of delegated
> > > prefixes in the ISPs routing domain?  Has a standard method/best
> > > practice emerged yet?  Routing protocols?  IPv6 RAs?
> > RAs really only apply to subnet local advertisement of routers and
> > the on-net prefixes in most implementations.
> >
> > I don’t think any of the various methods of using routing protocols,
> > static pre-routed blocks from which PDs are delegated, etc.  could
> > necessarily be called “standardized”, but there are probably a few
> > that are more popular than most of the others.
> >
> > Unfortunately, PD is really still in its infancy in terms of development
> > and real running code for complete implementations throughout any
> > sort of site hierarchy.
> >
> > Owen
> Thanks for the answer Owen!
>
> So it sounds like things are still in flux.  But it least it answers my
> main question of "have I missed something here"?
>
> Could you elaborate on the "local router seeing the PD answer" a bit?  I
> presume by "local router" you mean router acting as DHCPv6 relay?  Or do
> you mean the router which made the original request?

I mean the router that will deliver the PD to the requesting DHCPv6 client.

If the DHCPv6 server is on-net, then this will be the requesting client.
Otherwise, it will be the last relay router.

> Would it be fair to say that the RFCs only really talk about delegating
> the prefixes, and leave what to do with the prefixes themselves up to
> the implementer?

Yes… At least at this time. Some of the work in homenet might include
some suggestions for some implementations.


> I'm asking these questions because I'm doing a little class for some
> folks on IPv6 and this is one area where I couldn't find answers. 

Depending on your audience, I’d suggest that unless this is an advanced
IPv6 class, it’s probably one of those topics left for extra-curicular research.

Owen