Allocating fixed IPv6 addresses to hosts with multiple NICs

Frank Bulk frnkblk at
Thu Jan 13 05:27:59 UTC 2011

This doesn't really answer your question, but from an ISP perspective, since
most subscribers have a router at the edge of their network, both the IA and
PD will be stable.  

Sounds like a concern more in the enterprise space.


-----Original Message-----
From: at
[ at] On Behalf Of
John.Gibbins at
Sent: Tuesday, January 11, 2011 6:48 PM
To: dhcp-users at
Subject: Allocating fixed IPv6 addresses to hosts with multiple NICs

Is anyone handing out fixed IPv6 addresses with ISC DHCP?

With IPv4 we hand out IP addresses based on MAC addresses ("hardware
Ethernet" and "fixed-address" config entries).
With IPv6 we hand out IP addresses based on DUID ("host-identifier option
dhcp6.client-id" and "fixed-address6" config entries).

Our problem is that the DUID is system specific and not NIC specific.  To
uniquely specify a NIC, I need to specify both the DUID and the IAID, but I
can't find any way of specifying an IAID.  This effectively makes DHCPv6
useless for us on systems with multiple NICs.

Is there a way of handing out different predefined IPv6 addresses to for
different NICs on a host?

I'm hoping that I've missed something (obvious or otherwise).  If not, I'll
need to investigate alternate implementations.

John Gibbins
IT Security Operations (and IPv6 Evangelist)
CSIRO Information Management & Technology (IM&T)
Phone: +61 2 6124 1419  | Fax: +61 2 6124 1414 | Mob: 0419 605 562
John.Gibbins at | 
PO BOX 225, Dickson  ACT 2602
Do not let what you cannot do interfere with what you can do - John Wooden

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