ddns correct settings for dhcp when accepting client host names

Peter Rathlev peter at rathlev.dk
Tue Dec 3 20:18:08 UTC 2013

On Sun, 2013-12-01 at 09:55 +0000, Steve Brown wrote:
> If there was a way to configure dhcp to disregard the domain part if a
> client sent in its host name fully qualified I would much rather take
> this approach.

This would be simple if the DHCP server had an "index-of" string
function, alas it has not. _If_ it had you could do this:

  if (option host-name ~= "\.") {
    ddns-hostname = substring(option host-name, 1, 
                     index-of(option host-name, ".") - 1);
  } else {
    ddns-hostname = option host-name;

Does the client send an FQDN option perhaps? What happens if you try

  if (exists fqdn.hostname) {
    ddns-hostname = option fqdn.hostname;

> I also tried configuring the dhcp server with allow client-updates to
> see if it would make a difference. However this just led to a dynamic
> update entry in the zone file like this:

This points at the client being the problem. How did it end up having an
FQDN in "DHCP_HOSTNAME"? A bit of googling had me reading this:


which sounds like something changed between RHEL 5 and 6.

> I would really appreciate any pointers on the correct way to configure
> sending host names from clients  when using dhcp and bind for ddns
> thanks.

If it's RHEL you could ask RedHat what's happening. They're usually
competent people.


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