dual stack support in dhclient

David Horn dhorn2000 at gmail.com
Fri Apr 2 13:18:23 UTC 2010

On Fri, Apr 2, 2010 at 3:42 AM, Rudy Zijlstra
<rudy at grumpydevil.homelinux.org> wrote:
> Dears,
> Does dhclient have dual-stack support?
> I've been trying to find that, and could not. For a number of reasons i believe a lot of deployments will be fully or partially dual-stack for a number or years. Background:
> - many currently deployed devices do not support IPv6 and will not (cannot) be upgraded to support IPv6
> - There is going to be a transition time when you need to have both IPv6 and IPv4 access, as many (web)sites are still not IPv6 capable and it will take time for them to move to dual-stack support.
> My experiments of last week found that on linux the bottle-neck seems to be resolv.conf, where both the dhcp IPv4 client and the IPv6 dhcp client want to write it. As a result the contents are usually not correct.
> At the moment it is possible to work around this on a dual stack machine by ensuring the IPv6 dhcp client does not touch resolv.conf. Better would be if it would change only the IPv6 related parts, or if one dhcp client handles both IPv4 and IPv6.
> Any suggestions?

If NetworkManager is not your cup of tea, you can also look at
resolvconf or openresolv which will manage the /etc/resolv.conf file
in a more intelligent fashion.  It does require that you have a
dhclient-script that checks for and utilizes /sbin/resolvconf, but
that is trivial to setup.  This will allow multiple sources of dns
server information without stomping on each other.  You did not
mention what distro of linux you were using, so it is difficult to
give more specific information for your situation.

Google "openresolv" for one possible solution.

Good Luck.

---Dave Horn

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