Starting with the dhcp server in IPv6 mode

Fred Zwarts F.Zwarts at
Wed Sep 15 12:56:55 UTC 2010


We use the ISC dhcp server already for a few years for IPv4.
I just started to use the ISC dhcp server for some experiments with IPv6.
I downloaded and installed version 4.2.0. 

For the documentation I use the man pages dhcpd.8, dhcpd.conf.5 and dhcpd.leases.5
which I find in the server directory of the kit and the dhcpd-dhcpv6.conf file
in the doc/examples directory of the kit.

Most of the documentation in the man pages is still using IPv4 terminology.
I find it difficult to understand which part of the document refers to IPv4 only,
which part refers to IPv6 only and which part is applicable to both IPv4 and IPv6.
It is not clearly documented which of the statements/declarations/keywords
are accepted/rejected/ignored
1) only when the server runs in IPv4 mode
2) only when the server runs in IPv6 mode
3) both when the server runs in IPv4 or IPv6 mode.
In addition, in the example configuration I see options being used which are not found
in the man pages.

For example, my experiments show that the fixed-address6 statement is rejected
when the server runs in IPv4 mode, but the fixed-address statement is not
rejected when the server runs in IPv6 mode, but it is not clear to me what
fixed-address is assumed to do in IPv6 mode.

Further, my experiments seem to tell that the pool declarations do not work
for the server in IPv6 mode. (See my previous question about subnet6 and pools.)
So, I am not able to reject unknown clients from my dynamic address ranges.
range6 statements are rejected from within pools. This makes it unclear how
deny and allow are supposed to work, because the man page states
(about deny/allow/ignore unknown-clients):

       The  use  of  this  option  is  now  deprecated.   If you are trying to
       restrict access on your network to known clients, you should  use  deny
       unknown-clients;  inside  of  your address pool, as described under the

Another problem is that my experiments show that "hardware Ethernet" fails to
match the mac address in llt DUIDs. According to the release notes 
- The 'hardware [ethernet|etc] ...;' parameter in host records has been
  extended to attempt to match DHCPv6 clients by the last octets of a
  DUID-LL or DUID-LLT provided by the client.
The example configuration file says: 
        # This host entry is hopefully matched if the client supplies a DUID-LL
        # or DUID-LLT containing this MAC address.
If welcomed this as very good news, because it might allow us to use a 
common file with hosts declarations for both IPv4 and IPv6.
The words "attempt" and "hopefully", however, suggest that this does not work always,
but it is unclear to me under which circumstances this is supposed to work.
In my case the host matches when I use 
"host-identifier option dhcp6.client-id 00:01:00:06:14:20:e0:d3:00:0f:fe:4c:bd:f8;"
but it does not match when I use
"hardware ethernet 00:0f:fe:4c:bd:f8;",
although I can clearly see this mac address in the last octets of this LLT DUID.
These experiments makes that I feel that I have almost no progress in 
understanding the dhcpV6 server.
I have the feeling that I need some introductionary documentation about
the ISC dhcp server in IPv6 mode, which explains the differences and
similarities of configuration information for the server in IPv4 and IPv6 mode, 
so that I can make at least a start with a working configuration.
Is there such documentation?
If not, is there someone who can help with making a start?

Thanks in advance for suggestions,
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