problem updating dynamic dns from isc dhcpd

Cuttler, Brian (HEALTH) brian.cuttler at
Thu Feb 5 16:13:34 UTC 2015


Thank you, adding the zone info, and fixing the type in the key made a big difference.

I now have just a couple of machines in the new vlan, on the new dhcp server, but when I attempted to add another machine, I got the "no free leases" message.

Current config contains these lines, specific the the vlan, network I'm working on. I don't see the error. The first few machines had been in this address range before we brought this new dhcpd online, but the latest had not been in that address range before, would not have requested a specific preferred address. Is that related? Can you help point me to the fix?

Thank you,

zone {
key dhcpupdate;

zone {
key dhcpupdate;

#### default_vlan at ESP, Vlan 22
subnet netmask {
option routers;
        ddns-domainname = "";
        ddns-rev-domainname "";
#        range;
        pool {
                allow unknown clients;
                deny dynamic bootp clients;
#                range;
        option domain-name-servers,,,;
#        option domain-name-servers;

From: dhcp-users-bounces at [mailto:dhcp-users-bounces at] On Behalf Of Bill Shirley
Sent: Wednesday, February 04, 2015 11:14 PM
To: dhcp-users at
Subject: Re: problem updating dynamic dns from isc dhcpd

        zone ""   {

ddns-rev-domainname             "";
zone    { primary;    key DHCP_UPDATER; }


On 2/4/2015 4:27 PM, Cuttler, Brian (HEALTH) wrote:


Thanks for the zone suggestion in dhcp.

I think it was a number of issues, zone certainly pointed dhcpd to the correct dns server, I monkeyed a bit with ddns-* particularly when I found that I was able to get the forward record but the reverse came up as

Also, looking for mapping information I'd missed an error in the key map section, the "hac-md5" key wasn't working correctly. I'm apparently not as good a touch typist as I'd thought.

Follow up question.

What is the correct fix for the ddns-rev-domain?

I've currently got it set to "" but that means that all reverse records from all different zones will end up in the same PTR file. Is that typical or is there a better way do to this?

Thanks you,


-----Original Message-----

From: dhcp-users-bounces at<mailto:dhcp-users-bounces at> [mailto:dhcp-users-bounces at] On Behalf Of Simon Hobson

Sent: Wednesday, February 04, 2015 3:21 PM

To: Users of ISC DHCP

Subject: Re: problem updating dynamic dns from isc dhcpd

"Cuttler, Brian (HEALTH)" <brian.cuttler at><mailto:brian.cuttler at> wrote:

When DHCP attempts to update the DNS tables I get the following error.

Dhcpd: unable to add forward map from to not found

Do you have zone statements in your dhcpd.conf ?

If not using secure updates, you can just rely on having the zones correctly set up (correct SOA record) and dhcpd will find the master server from the SOA record. But since you are using signed updates, you must specify zones in dhcpd.conf - the syntax is *almost*, but not quite, identical to that in named.conf.


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