DHCPv6 and DDNS

[Philippe Clérié]

On 06/29/2015 04:53 PM, Simon Hobson wrote:
> Chris Buxton <clists at buxtonfamily.us> wrote:
>
>>> It took a while but I believe I have found my problem. It appears that the DHCP server does not update DNS records for static leases. DNS does get updated for clients that get their addresses from the subnet range.
>>>
>>> Can anyone confirm that please?
>>
>> Correct, that is the default behavior. It can be changed with a configuration option. Iirc, the option is called "update-static-leases".
>
> Just for completeness, be aware that IIRC it will create the DNS entries but doesn't delete them. That's because a static lease (host declaration with fixed-address statement) doesn't create a lease record, so the server actually has no comprehension of the "lease" expiring.
>
>
> Philippe Clérié <philippe at gcal.net> wrote:
>
>> I thought it might be useful to put up my client config.
>> ...
>> do-forward-updates on;
>
> Whether that works or not depends on several factors.
> Firstly, the DHCP server can over-ride it and do the forward updates.

Understood. But note, one, that it was always my intention for the 
server to do the updates, and two, that the logs show that the source 
for the updates is the server itself as configured in dhcpd6.conf.

The DHCPv4 server does not need those lines, so v6 shouldn't either.

> Secondly, the DNS server may or may not have restrictions (either by IP/net or keys) configured for zone updates. If the DHCP server allows it, but the DNS server does not - it will just fail.

The DNS server is configured to allow updates from both IPv4 and IPv6 
networks. (I was being intentionally lazy expecting to restrict that 
once I had things working.) Anyway, I can update the DNS from the server 
using nsupdate. The DHCP server does the updates for IPv4 (no problems 
at all) and for IPv6 when the address is allocated from the given subnet 
range.

BTW the DHCP config file is in my first post at the top of this thread.

Here's the scenario:

- The DHCP server is configured using the config file mentioned above.
- The DHCP client is configured using the config file just posted.
- On boot, the client is assigned the fixed IPv6 address but does not 
update DNS. There is not a trace of an attempt at updating DNS. Not in 
syslog and not in tshark.
- Now, in DHCP server config, comment out the static address.
- On boot, the client is assigned an address from the dynamic range and 
updates the DNS server.

For what it's worth, there are more problems.

- There's a race condition with DAD (There's a work around for that, but 
it was supposed to have been fixed - in Debian.).

- DHCPv4 and v6 don't seem to agree on what DUID each is using (not sure 
what the story is on that. It's not a priority presently.)

- I'm now trying out updates from the client (just adding "allow 
client-updates" to the server configuration), and my client just hangs 
on boot, never replying to the Advertise message from the server. 
Investigation is ongoing.

Regards,

-- 
Philippe

------
The trouble with common sense it that it is so uncommon.
<Anonymous>