[Kea-users] IA_PD without IA_NA and reserved Prefixes

Wido den Hollander wido at widodh.nl
Mon Apr 25 19:21:01 UTC 2016


> Op 25 april 2016 om 17:49 schreef Marcin Siodelski <marcin at isc.org>:
> 
> 
> 
> 
> On 20.04.2016 20:07, Wido den Hollander wrote:
> > 
> > 
> >> Op 20 apr. 2016 om 19:17 heeft Marcin Siodelski <marcin at isc.org> het volgende geschreven:
> >>
> >>
> >>
> >>> On 20.04.2016 07:39, Wido den Hollander wrote:
> >>>
> >>>> Op 20 april 2016 om 16:06 schreef Wido den Hollander <wido at widodh.nl>:
> >>>>
> >>>>
> >>>> Hello,
> >>>>
> >>>> My use-case is where I want to run a DHCPv6 server which does IA_PD, but
> >>>> doesn't
> >>>> do IA_NA.
> >>>>
> >>>> The clients in this case obtain their address through SLAAC and additionally
> >>>> can
> >>>> get a prefix through IA_PD.
> >>>>
> >>>> Additionally I only want assigned prefixes to be allowed. Only if a
> >>>> reservation
> >>>> is present I want to hand it out. Otherwise no prefix is assigned. That part
> >>>> seems to work by using the 'out-of-pool' mode for reservations.
> >>>>
> >>>> In Kea I can't get this configured since it always requires a subnet.
> >>>>
> >>>> "subnet6": [
> >>>>        {
> >>>>            "subnet": null,
> >>>>            "interface-id": "VLAN709",
> >>>>            "reservation-mode": "out-of-pool",
> >>>>            "reservations": [
> >>>>                {
> >>>>
> >>>> This doesn't work, the same as leaving 'subnet' out of the configuration.
> >>>>
> >>>> Is this possible with Kea?
> >>>
> >>> I actually found out that this already works. Just define a 'subnet', but do not
> >>> define a 'pool' inside the subnet6 section.
> >>>
> >>> My clients are now able to obtain a prefix through IA_PD but never get a answer
> >>> for IA_NA:
> >>>
> >>> [kea-dhcp6.alloc-engine/1856] ALLOC_ENGINE_V6_ALLOC_FAIL
> >>> duid=[00:01:00:01:1e:94:17:e8:06:d4:36:00:04:87], tid=0x189a81: failed to
> >>> allocate an IPv6 address after 0 attempt(s)
> >>>
> >>> Wido
> >>
> >> Hi Wido,
> >>
> >> From your second email it sounds that you were able to configure Kea to
> >> do what you want. Do you need any more assistance on this?
> >>
> > 
> > Yes, it works now. However, it would be nice if you could omit the subnet in the configuration.
> > 
> > This way Kea knows you only use it for IA_PD and will not respond on IA_NA.
> > 
> 
> Even if you're not doing IA_NA, the "subnet" declaration is still
> required (without address pools as you say), because you need to be able
> to define "pd-pools" (pools for prefix delegation). The "pd-pools" are
> defined per-subnet.
> 

Yes, I know. But without IA_NA the "subnet" is never used. With my out-of-pool reservations I don't use the pool at all. The pool where I hand out PD from is not even in the subnet.

Technically the 'subnet' is just dummy. I could insert 2001:db8::/64 just to enter something.

Wido

> Marcin


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