[kea-dev] link-local-only operation

Templin, Fred L Fred.L.Templin at boeing.com
Fri May 15 16:12:55 UTC 2015


Hi Tomek,

> -----Original Message-----
> From: Tomek Mrugalski [mailto:tomasz at isc.org]
> Sent: Friday, May 15, 2015 9:02 AM
> To: Templin, Fred L; kea-dev at lists.isc.org
> Subject: Re: [kea-dev] link-local-only operation
> 
> On 15.05.2015 17:50, Templin, Fred L wrote:
> >> This will cause Kea to communicate over eth0 using link-local addresses
> >> only.
> >
> > Yes, that is what I want. This is what I am already doing.
> >
> >> It will delegate /64 prefixes out of its 2001:db8:1::/56 pool.
> >
> > Good. Also what I want.
> >
> >> If clients ask for addresses (send IA_NA), they will get NoAddrsAvail in
> >> their IA_NA responses.
> >
> > Should never happen, so it is fine.
> >
> >> Does that address your need?
> >
> > The concern I have is this part:
> >
> >         > # That doesn't really matter. Kea will be unhappy if there's no
> >         > # subnet parameter.
> >         >       "subnet": "2001:db8::/64",
> >
> > That is what I mean by "burning a prefix". I don't want to have to
> > associate any global IPv6 prefix with the eth0 interface in any way;
> > I want it to be purely link-local just like for "ping6 -I eth0 fe80::1',
> I see. This part is not really used if you specify that the subnet is
> reachable directly. Feel free to replace it with "subnet": "fe80::/10".
> I haven't tested it, but it should work.

Yes, that is exactly what I need! Unfortunately, I will not be able to test
until the 2-message exchange for DHCPv6 PD is ready for testing. But,
I will save this change in my kea config file and be ready to test once
we get to that phase.

> > So, I would like to have a "no subnet" model where the only
> > guidance to kea is the interface name itself.
> When you think about it, the proposal above is closer representation of
> the actual network than what you're proposing. It doesn't have any
> global IPv6 prefix associated with it.

Good. This should address the need.

Thanks - Fred
fred.l.templin at boeing.com

> Tomek
> 
> p.s.
> Note to other users that may stumble upon this post some time later. In
> general, it is a bad idea to tell your DHCPv6 server to manage
> link-local addresses. And that's NOT what we're trying to do here. The
> subnet fe80::/10 is simply a representation of the network topology and
> there are no address pools defined in it, so the server will not
> delegate any addresses out of it. On the other hand, the server will
> delegate prefixes, but that's ok. There is no requirement for the server
> to match delegated prefixes to any prefix configured locally.



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