Allocating fixed IPv6 addresses to hosts with multiple NICs

John.Gibbins at John.Gibbins at
Fri Jan 14 02:47:22 UTC 2011

Hi Frank,

Thanks for the link to the previous thread (I'm fairly new to this list).  I agree with most of the complaints in the thread, but have accepted that we need to live with DHCPv6 as it is designed.  Any change isn't going to happen in any useful timeframe.

I'm trying to make DHCPv6 work as I think it was intended to work (not how I'd like it to work).  One of the messages in the thread (, extract below) suggested allocating a dynamic lease and then extracting the DUID from the lease database.  This clearly identifies that the dynamic lease assignment is based on the IA-NA which consists of the IAID concatenated with the DUID.  What I want to do is assign fixed IP addresses based on this same concatenation and not just the DUID.

To me this seems fundamental to DHCPv6, so I find it hard to believe that ISC DHCPD doesn't support it.  Can someone confirm that this is not supported or tell me what I've missed?

David_Hankins at said:
> Here's an example;
>   ia-na "@@\026v\000\001\000\001G`t$\000\014v\026@@" {
> Take off the fourst four octets. (@ @ \026 v), which are the
> IA-NA's IAID (we concat the IAID and DUID to form a unique identity
> for one this case, the client has used its last four
> MAC address octets as its IAID).
> Then use it in a host clause thusly:
>   host-identifier option dhcp6.client-id
>                         #    DUID-LLT - ETH -- TIME --- ---- address ----
>                                 00:01:00:01:47:60:74:24:00:0C:76:16:40:40;

John Gibbins
IT Security Operations (and IPv6 Evangelist)
CSIRO Information Management & Technology (IM&T)
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-----Original Message-----
From: at [ at] On Behalf Of Frank Sweetser
Sent: Thursday, 13 January 2011 11:00 PM
To: dhcp-users at
Subject: Re: Allocating fixed IPv6 addresses to hosts with multiple NICs

On 1/13/2011 3:19 AM, John.Gibbins at wrote:
> Thanks Frank,
> We are an Enterprise.  We want to have control over what machines are allowed
> on our network and to be able to easily identify them by their IP addresses.
> EUI-64 and MS random addresses used by SLAAC make this hard so we want to use
> DHCPv6 to hand out addresses only to known machines.  We have a /32 block so
> we have an obscene number (2^96) of addresses to play with.

This issue has been brought up before.  Take a look at for one of 
the longer discussions on it.

Frank Sweetser fs at  |  For every problem, there is a solution that
WPI Senior Network Engineer   |  is simple, elegant, and wrong. - HL Mencken
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