force DDNS update

Carl Karsten carl at
Mon Apr 23 01:10:47 UTC 2007

My dhcp/ddns setup does almost exactly what I want it to.  I think I have one 
little kink to work out:  when the IP of a box changes, bind doesn't pickup the 

If you are wondering: why does the IP change?  good Q.  I have a few A's:

1. duel boot box, both boots have the same hosthame (perhaps I should change 
this)  I boot into Win, it sends hostname=foo and gets IP  I shut that 
down (it does not release the lease on .1) and boot into linux, it sends 
hostname=foo and gets IP

2. I move a box from the IP pool to a fixed IP using dhcp.conf
fixed-address ;

3. swap nic, so new mac.

4. magic?

In any event, anytime dhcpd tells bind foo=X, I don't want bind to argue.  I 
want it to take the new IP and make it so.

the ddns part of /etc/dhcp3/dhcpd.conf:

ddns-updates on;
ddns-update-style interim;
do-forward-updates on;
ddns-domainname "";
ddns-rev-domainname "";
update-static-leases on;
# ddns-ttl 7200;

         algorithm HMAC-MD5.SIG-ALG.REG.INT;
         secret ZiO1XpvhIDVLRsvnBk9+Qw==;

zone {
         primary localhost;
         key DHCP_UPDATER;

zone {
         primary localhost;
          key DHCP_UPDATER;

guessing the only important part of bind.conf:

zone "" {
         type master;
         file "/etc/bind/";
         allow-update { key DHCP_UPDATER; };

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