problem updating dynamic dns from isc dhcpd

Cuttler, Brian (HEALTH) brian.cuttler at
Wed Feb 4 18:53:26 UTC 2015

Hello dhcpd users,

I'm sorry to have to ask, I've found some very helpful web pages, but I've been unable to get the syntax quite right...

I am running a test system to prototype how we want to do our dhcp moving forward.

To that end I've built a test system on Centos 7, installed isc dhcp and named, both current versions.

DHCP is currently able to hand out addresses in the designated zone, and I am able to update DNS using # nsupdate.

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

Dhcpd: unable to add forward map from to not found

The zones in the named.conf look like this

zone "" in {
        type master;
        file "db.esp22";
        allow-update { key dhcpupdate; };

zone in {
        type master;
        file "db.esp22-ptr";
        allow-update { key dhcpupdate; };

The stanza I'm working with in dhcpd.conf is probably where the problem is, I suspect I do not actually understand the structure of the dhcpd.conf file

I know that putting the ddns-domainname in the stanza is an error, its global, but the domain is "" and I'd thought that the dynamic range needed to be limited to a subset of the domain.

Not sure how to resolve the issue and need a little help.

I can include more detail, and will post the results when completed, any help would be appreciated.

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

Thanks in advance,

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