[kea-dev] link-local-only operation

[Tomek Mrugalski]

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.

> 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.

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.