dhclient and dynamic DNS

[Joel Goguen]

On 7/28/07, Noah <admin2 at enabled.com> wrote:
> Hi there Ubuntu list,
>
> I am having a bit of trouble with getting dynamic DNS working.  I have
> dynamic DNS configured in my dhclient.conf configuration like below.
> But on the client side the error shows that I am sending the update to
> the IP address of the client server instead of the IP address defined by
> the "primary" line in the "zone domain.com" stanza.
>
> all messages revise the real hostname, IP address, and domain name.  I
> am hoping somebody can catch my misconfiguration.
>
> so the error looks as follows:
>
> --- snip ---
>
> Jul 28 18:57:13 real.host dhclient: Can't update forward map
> real.host.domain.com. to <ip_address_of_real.host.domain.com.>: timed out
>
> --- snip ---
>
> cat /etc/dhcp3/dhclient.conf
> send fqdn.fqdn "real.host.domain.com.";
> send fqdn.encoded on;
> send fqdn.server-update off;
>
> key real.host.domain.com {
>     algorithm HMAC-MD5;
>     secret "secret";
> };
>
> zone domain.com {
>      primary <domain_name_server_ip>;
>      key "real.host.domain.com";
> }
>
> supersede domain-name "domain.com home.domain.com";
> prepend domain-name-servers 127.0.0.1;
> request subnet-mask, broadcast-address, time-offset, routers,
>          domain-name, domain-name-servers, host-name;
>
>
>
> --- snip ---
>
> Cheers,
> Noah
>
>
>
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man 5 dhclient.conf:

DYNAMIC DNS
       The client now has some very limited support for doing DNS updates when
       a  lease  is  acquired.   This is prototypical, and probably doesn't do
       what you want.   It also only works if you happen to have control  over
       your DNS server, which isn't very likely.

Note the parts about it probably not doing what you want, and only
working if you have control over your DNS server.  In other words, if
you're working with a DNS server inside your own network that you've
configured to allow you to update in this manner, then we fall back to
the man page saying this probably won't do what you want, but maybe
someone else here has it working.  OTOH, if you're trying to do this
anywhere you're at in random networks (university, cafe, buddy's
place, etc) then I doubt you'll get any success since you need to be
updating a DNS server that you control.

If you're trying to do this outside your own home (or even inside if
this is too much trouble) I would recommend picking up a client
updater from DynDNS.  That way, you won't accidentally update your
DynDNS with a private internal IP :)

-- 
Joel Goguen
http://jgoguen.net/