Leasing addresses from a delegated prefix

Aaron Murrihy aaron_m at aaron-m.co.nz
Mon May 10 00:00:33 UTC 2010

Thanks for the reply.

Sorry, I should have informed you of the versions I was using. The ISP
machine is version 4.2.0b1, and my CPE machine is using 4.1.1 as that
version has been ported to openWRT.

Yes, the dhcp-options manpage does say that about "option dhcp6.ia-pd
string;", however after reading this post to a mailing list at
http://lists.cluenet.de/pipermail/ipv6-ops/2009-December/002768.html I
believe that leaving it with this explanation was an oversight.

The manpage in dhcp-4.2.0b1 describes this option in this way:

 option dhcp6.ia-pd string;

         The  ia-pd option is manufactured by clients and servers to
create a Prefix Delegation binding - to delegate an IPv6 prefix to the
client.  It is not directly edited
         in dhcpd.conf(5) or dhclient.conf(5), but rather is
manufactured and consumed by the software.

But this option is used "to delegate an IPv6 prefix to the client"
which I already have managed to do. This is taken from my
dhclient6.leases file:

lease6 {
  interface "eth1";
  ia-pd 27:00:03:db {
    starts 1273449002;
    renew 0;
    rebind 0;
    iaprefix 2000:1:1:e00::/56 {
      starts 1273449002;
      preferred-life 375;
      max-life 600;
  option dhcp6.client-id 0:1:0:1:13:76:8:b9:0:90:27:0:3:db;
  option dhcp6.server-id 0:1:0:1:13:57:d2:7f:0:b:db:42:0:84;

As you can see, I have been delegated the prefix 2000:1:1:e00::/56,
but what I need to do now is run a dhcp server on that machine which
can take a /64 from this prefix and start subleasing addresses to end

Has this functionality been implemented yet, or will my best bet be
either add the functionality to the dhcp server myself or write a
script to parse the lease file and change the dhcpd6.conf file

Thanks for any assistance.

Aaron Murrihy
WAND Group, University of Waikato

>Date: Fri, 7 May 2010 15:48:47 -0700
>From: Jeff Haran <jharan at Brocade.COM>
>Subject: RE: Leasing addresses from a delegated prefix
>To: Users of ISC DHCP <dhcp-users at lists.isc.org>
>      <D67825C5985D0647BE40A5F5B0B70D110D4063CB71 at HQ-EXCH-7.corp.brocade.com>

>>From: dhcp-users-bounces+jharan=brocade.com at lists.isc.org [mailto:dhcp-users->bounces+jharan=brocade.com at lists.isc.org] On Behalf Of Aaron Murrihy
>>Sent: Friday, May 07, 2010 2:07 PM
>>To: dhcp-users at lists.isc.org
>>Subject: Leasing addresses from a delegated prefix

>>I am working on a project for the final year of my Bachelor of Computing and Mathematical Sciences degree,
>>and I decided I would develop a firmware for a CPE that performs only IPv6, no dual-stacking. (I will most
>>likely eventually use openWRT, but for now I am just using a linux machine.)
>>I have successfully configured the DHCP server on my ISP emulating machine to lease a prefix to my CPE
>>emulating machine (Both the DHCP client and server are using ISC's implementation of DHCP). However, now I
>>wish to use part of that leased prefix to sublease addresses to other hosts, but I have been unable to
>>discover how to do this. I have read all the man pages, and searched google extensively to no avail. Is there
>>a way to do this already built into DHCP, or will I need to either add the feature myself or write scripts to
>>parse the lease file and set the configuration file of the DHCP server of the CPE?

>According to the 4.1.1 dhcp-options man page:

>      option dhcp6.ia-pd string;

>        The ia-pd option is manufactured by clients and servers to create  a
>         Prefix  Delegation  binding  -  to  delegate  an  IPv6 prefix to the
>         client.  There is not yet any support for prefix delegation in  this
>         software, and this option is provided informationally only.

>4.1.1 is latest production release. Perhaps the 4.2.0b1 beta has it.

>Also, please post in plain text.

>Jeff Haran
>Brocade Communications

More information about the dhcp-users mailing list