Prefix delegation to sub nets

Brian Carpenter brian.e.carpenter at
Mon Jun 28 11:10:00 CEST 2021

Is HNCP available for the various Linux distros?
If not, it has to be PD, I think.

    Brian Carpenter
    (via tiny screen & keyboard)

On Mon, 28 Jun 2021, 20:51 Ole Troan, <otroan at> wrote:

> > On 27 Jun 2021, at 23:07, Brian E Carpenter <brian.e.carpenter at>
> wrote:
> >
> > That doesn't work. B needs to get its own /64 prefix(es) from A via
> DHCPv6-PD ( That's what
> DHCPv6-PD is for. So A will indeed need to be a DHCPv6 server on its
> downstream interfaces.
> To the extent it matters, it’s not what DHCP PD was designed for.
> HNCP does internal prefix assignment in a network.
> Now, if you were to use DHCP PD for this, I would recommend a single PD
> server in the network (on A).  DHCP PD clients on all internal routers.
> Either DHCP relays or more simply each internal router PD client configured
> with the address of the PD server directly. Then an IGP to advertise
> prefixes.
> The PD clients should request individual /64s for each of their downstream
> interfaces.
> This scheme does not work great in networks with loops or multiple routers
> on a link. If using DHCP relays you manually have to make a spanning tree.
> And you risk links being assigned multiple prefixes.
> HNCP solves all of this.
> Cheers
> Ole
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