DDNS Updates on lease expire.

Mark Mc Nicholas markmcn at section9.ie
Wed Aug 17 12:00:48 UTC 2016

Hi Simon,
Thanks, I didn't want to waste people's time with config's until I
confirmed if this was normal.
Below are the config's of DHCPD & Bind,
I've edited the keys since posting publicly.
I have no logs from DHCPD indicating a release of an IP. DHCP & DNS are
running on different boxes however there is no known communication issue
between them.
The only proof I can show from logs is that it updates A records and PTR
Please let me know if I have missed something
Thanks for the help
Kind Regards

====DHCPD Config====

ddns-updates on;
ddns-update-style interim;
update-static-leases    on;
key sun-key { algorithm hmac-md5; secret "123456789";}
allow unknown-clients;
use-host-decl-names on;

zone    i.home.ie.{
        primary moto.i.home.ie;
        key sun-key;

# Common to all subnets
option domain-name "home.ie";
default-lease-time 1800;
max-lease-time 14400;
allow unknown-clients;

subnet netmask {
        default-lease-time 1800;
        max-lease-time 14400;
        option routers;
        option domain-name-servers, ;
        option domain-name "i.home.ie";
        option domain-search "i.home.ie";
        option ntp-servers,;
        ddns-domainname "i.home.ie.";
        ddns-rev-domainname "in-addr.arpa.";

        host skynet09{
                hardware ethernet AC:CF:23:8D:10:60;
                ddns-hostname "skynet009";

====Bind Config====
key "sun-key" {
      algorithm hmac-md5;
      secret "123456789";

options {
        listen-on port 53 {; };
        #listen-on-v6 port 53 { ::1; };
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { any; };
        allow-recursion { PermitRecursion; };
        recursion yes;

        dnssec-enable yes;
        dnssec-validation yes;
        dnssec-lookaside auto;

        /* Path to ISC DLV key */
        bindkeys-file "/etc/named.iscdlv.key";

        managed-keys-directory "/var/named/dynamic";

logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;

        zone "i.home.ie" {
                type master;
                file "/etc/named/i.home.ie";
                allow-update { key sun-key; };
                allow-transfer { RFC1918; };
                notify yes;

Bind Logs of an Update

named[1563]: client updating zone 'i.home.ie/IN': update
unsuccessful: skynet001.i.home.ie: 'name not in use' prerequisite not
satisfied (YXDOMAIN)
named[1563]: client signer "sun-key" approved
named[1563]: client updating zone 'i.home.ie/IN':
deleting rrset at 'skynet001.i.home.ie' A
named[1563]: client updating zone 'i.home.ie/IN': adding
an RR at 'skynet001.i.home.ie' A
named[1563]: client signer "sun-key" approved

DHCP Logs for the same device
dhcpd[6271]: DHCPREQUEST for from ac:cf:23:8d:77:56 via eth0
dhcpd[6271]: DHCPACK on to ac:cf:23:8d:77:56 via eth0
dhcpd[6271]: Added new forward map from skynet001.i.home.ie. to
dhcpd[6271]: Added reverse map from to

On Wed, Aug 17, 2016 at 12:34 PM, Simon Hobson <dhcp1 at thehobsons.co.uk>

> Mark Mc Nicholas <markmcn at section9.ie> wrote:
> > I'm wondering should DHCPD update DNS to remove an expired entry?
> Yes it should.
> It might help if you posted your config, and log file entries relevant to
> an event.
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users

Begin at the beginning,and go on till you come to the end: then stop.
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