Trying to configure ipv4 and ipv6 addresses on hosts using one dhcp server fails.

Timothy Stoddard testoddard at
Tue Aug 24 18:50:00 UTC 2010

On Tue, Aug 24, 2010 at 1:34 PM,  <sthaug at> wrote:
>> Now, when running dhcp for both dhcpv4 and v6 clients on the same
>> server, dhcp service does not allow for an exsisting v4 record to be
>> updated with v6:
> As far as I know, ISC DHCP cannot handle both IPv4 and IPv6 using the
> same dhcpd process. You need two instances of the process. See this
> section from the dhcpd man page:
>  The server either operates as a DHCPv6 server or a DHCP server, but not
>  both  at  the same time. To run as a DHCPv6 server, use the -6 flag. To
>  run as a DHCP server, use the -4 flag. If neither is used, the  default
>  is to run as a DHCPv6 server.

I have experienced the same thing.  When the DHCP server tries to
update the A record of a dual-stacked client the TXT records seem to
get in the way.  Could this have something to do with DHCPv6 not using
mac addresses and using DUIDs instead?  I wonder how the DHCID is
computed for a IPv6 TXT record?

We have two sets of DHCP servers which handle either IPv4 or IPv6 as
the first response mentioned.


> Steinar Haug, Nethelp consulting, sthaug at
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> dhcp-users at

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