How to trigger a DNS update?

John Hascall john at
Fri May 11 16:16:53 UTC 2012

> >host 0f1f9faf2fcc {
> >         hardware ethernet 0f:1f:9f:af:2f:cc;
> >         ddns-hostname "joe-blah";
> >         ddns-domainname "";
> >         option domain-name "";
> >}

> >Not unexpectedly, when dhcpd is restarted with this new config file,
> >this doesn't actually cause DHCP to change the hostname in DNS.
> >It doesn't even appear that it happens when the lease is renewed.

> Correct. The default is that these names will not be added at all by 
> the DHCP server - but there's an option (whose name I don't recall) 
> to do updates for static assignments

   (If I'm understanding your terminology), these are not "static"
   assignments (i.e, there is no "fixed-address" in their definition):
   they get lease entries from a pool and get written to the lease file
   and DHCP does set the DNS entries when a lease is created -- but
   it looks to me like it doesn't update them -- it seems like maybe
   the lease has to actually expire, then they are deleted, and if
   the machine shows up again, it gets re-created with the new values.
   Of course, in our environment lots of machines are on 24x7 ...


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