Sebastián Fritz sfritz at stechs.com.ar
Tue Sep 23 20:26:18 UTC 2014

Hi Tomek,
                  Thank you for your help. I believe that,  there is not
any problem in assign an IA_NA  at the DOCSIS eRouter’s WAN side and a
different range prefix IAPREFIX at the DOCSIS eRouter’s LAN side. In this
way, I could have  an  smaller prefix to only assign IA_NA at the WAN side
and a bigger subnet to assign IAPREFIX at the LAN side.
                   Knowing  that DOCSIS Spec suggests to do the assignment
(IA_NA) and DHCPv6 prefix delegation (IA_PD) in a single DHCPv6 session. Do
you plan to support it in the future?.  Below, there is the references with
this recommendation.

“CM-SP-eRouter-I13-140729” -( Section 8.3 - Obtain IPv6 address and other
configuration parameters),  (

“...DHCPv6 address assignment (IA_NA) and DHCPv6 prefix delegation (IA_PD)
SHOULD be done as a single DHCPv6 session....”

Thanks again for your time!


2014-09-23 8:39 GMT-03:00 Tomek Mrugalski <tomasz at isc.org>:

> On 23.09.2014 01:24, Agustín Bertamoni wrote:
> > According to docsis scenario, we need to assign IA_NA and  IA_PD to
> > erouters at the same time, but the NA (non-temporary addresses)
> > candidate and the IAPREFIX not necessary must be in the same prefix, so
> > the “pool” and “pd-pool” are not in the same subnet.
> > As a result of the tests, this seems not to be supported and we see that
> > first selects a class-based available subnet and PD that is within it.
> > Is this analysis correct ?
> Yes. The assignment process more or less looks like following:
> 1. parse incoming packet
> 2. assign packet to a class if appropriate. Right now it simply takes
> content of the vendor-class identifier (DHCPv4) or vendor class
> (DHCPv6). The class is specified on a per packet basis.
> 3. a subnet is selected for incoming packet. Normally it is done based
> on relay IP address and/or interface-id inserted by relay, but you can
> also allow/forbid specific client class from a given subnet.
> 4. Leases are assigned from the selected subnet. Each lease type (IA_NA
> or IA_PD) is processed separately, but to assign both of them, you need
> to have both pool and pd-pool defined.
> So if you want to have both IA_NA and IA_PD assigned in the same
> transaction, it is currently not supported. But are you completely sure
> that's what you really want? One of those resources assigned (either
> address or prefix) will be topologically incorrect.
> Tomek
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