DDNS and DHCP updates failing

Gareth Ansell ccx264 at coventry.ac.uk
Wed Jan 12 11:45:43 UTC 2005


This may be a bit off topic, as it is to do with ISC dhcpd, not bind,
but I couldn't find a group for dhcpd, and the topics are closely

We have a DHCP/DDNS setup (bind-9.2.3 and dhcp-3.0pl2 on a slackware
which has been working OK, but it has now stopped. There have been no
updates to the servers, and no modifications (which I know of) to the
configuration files.

The problem appears to be that DHCP is no longer sending out update
messages to the DNS server.  The DNS server appears to be working OK,
and will update using nsupdate OK.  The really curious thing about
this is, that if you grep the log files, the DHCP does do the
occasional update, about 1 a day or so.  However, it should be doing
much much more than this.

This is an example from the named.conf file

zone "dhcp.coventry.ac.uk" {
        type master;
        file "dhcp/dhcp.coventry";
        allow-update {localhost; key DHCP-DNS.;};
        allow-transfer { key dns1-dns2.; xxx.xxx.xxx.xxx;
xxx.xxx.xxx.xxx;  };

This is what we have in the dhcpd.conf for the above zone

ddns-updates true;
ddns-update-style interim;
ddns-domainname "dhcp.coventry.ac.uk";
ddns-hostname = pick(host-decl-name, option host-name);
ddns-ttl 86400;
deny client-updates;

zone dhcp.coventry.ac.uk. {
        key DHCP-DNS.;

I have turned on the debugging for named, which showed that it was
not receiving any update messages, and a tcpdump showed that none
were being send by dhcp.

Has anyone experienced this before?  Does anyone know how to ramp
up the logging on the DHCP server to try to get any more info, is
this a really obvious config problem which I am missing?

Any help greatly appreciated.

Gareth Ansell

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