DDNS update not sent on initial DHCP offer/request/ack

[Forman, Jeffrey]

On Wed, Dec 7, 2016 at 11:11 AM, /dev/rob0 <rob0 at gmx.co.uk> wrote:

> On Wed, Dec 07, 2016 at 10:33:02AM -0500, Forman, Jeffrey wrote:
> > I've got a fairly standard setup here, ISC dhcpd handing out IPv4
> > address, updating a DNS zone handled by BIND with those hostnames.
> > Though it seems lately (perhaps it's always been this case?) that
> > the first time a new host comes up and requests an IP from the dhcp
> > server, BIND is not notified of the new hostname and IP address. I
> > have to reboot the client and then, on the subsequent request/ack
> > cycle, is DNS updated. So my question is, why do I have to reboot
> > the clients to get dhcpd to update bind? Is something misconfigured
> > in my DHCPD to not do the intial update, or is it something
> > client-side that is needed?
>
> What you showed us suggests it's a client issue.
>
> > Infrastructure:
> >
> >    - dhcp server os: OpenBSD 6.0 on amd64 ($OPENBSD in the below logs)
> >    - dhcpd version: isc dhcpd 4.3.4
> >    - bind version: isc bind 9.10-4p2
> >    - client OS: CoreOS (though I also run ubuntu and OSX locally as well)
> >    ($COREOSCLIENT in the below logs)
> >
> > From the DHCPD logs, the initial request:
> >
> > Dec  7 06:25:49 $OPENBSD dhcpd: DHCPOFFER on 10.10.2.245 to
> > 52:54:00:18:f7:fb via vlan12
> >
> > Dec  7 06:25:49 $OPENBSD dhcpd: DHCPREQUEST for 10.10.2.245 (10.10.2.1)
> > from 52:54:00:18:f7:fb via vlan12
> >
> > Dec  7 06:25:49 $OPENBSD dhcpd: DHCPACK on 10.10.2.245 to
> 52:54:00:18:f7:fb
> > via vlan12
>
> I don't see in that where any hostname was provided.
>
> > I reboot the client, and then:
> >
> > Dec  7 06:27:59 $OPENBSD dhcpd: DHCPREQUEST for 10.10.2.245 (10.10.2.1)
> > from 52:54:00:18:f7:fb via vlan12
> >
> > Dec  7 06:27:59 $OPENBSD dhcpd: DHCPACK on 10.10.2.245 to
> 52:54:00:18:f7:fb
> > (coreE3) via vlan12
>
> Here "coreE3" is the hostname ... was this a munging failure meant to
> be "$COREOSCLIENT"?
>

yes

>
> > 07-Dec-2016 06:27:59.177 update-security: info: client
> 10.10.2.1#28804/key
> > $TSIG-KEY: signer "$TSIG-KEY" approved
> >
> > 07-Dec-2016 06:27:59.177 update: info: client 10.10.2.1#28804/key
> > $TSIG-KEY: updating zone 'dns.zone.net/IN': adding an RR at
> '$COREOSCLIENT'
> > A 10.10.2.245
>
> "Zone.net" is not a good choice for a home zone name.  If you're
> simply hiding the real name behind "zone.net", use "example.net"
> which has been set aside for such use.
>

Nod. I can do so in later examples if necessary.


>
> [snip]
> > What am I missing here? Why does it require a restart of the client
> > to get the dns entry added?
>
> Apparently it did not provide a hostname to add to DNS.
>

Huh. Apparently even if the host knows its hostname upon install. :/

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