Force DDNS updates?

Shawn Routhier sar at
Mon Sep 14 19:45:27 UTC 2015

Check out the update-optimizaton option in the dhcpd.conf man page

By default this is enabled and tells the server to only do DDNS updates if it thinks it needs to,
if you change it to disabled (or false) the server will do DDNS updates on each client renew.

This would require you to update your config and restart your DHCP server.

But you might want to look at your lease files a bit to try and see what the DHCP server thinks
has already happened with the DDNS entries.  If the lease entries already have DDNS information
then it implies your DNS server lost the information somehow and turning off the optimization should
help.  If the lease entries don’t have DDNS information  it might mean that the DHCP server
doesn’t think there is a DNS name to update and the optimization flag may not help.


> On Sep 14, 2015, at 12:17 PM, Gregory Sloop <gregs at> wrote:
> So, I'm not sure how this occurred, but I have dhcp clients/leases which exist, but which have no DDNS entry. [And normally, as DHCPD allocates IP addresses, it also updates/creates the DDNS entries for those hosts.]
> But, now, until they get a new IP, they'll continue to not attempt to update their DDNS records [which don't exist] and so unless I somehow force the clients to new IP addresses they'll never get their DDNS records created/updated.
> Now, how this happened, I'm not sure. 
> And while it might be nice to know, the more pressing problem is how to fix it.
> I know I can, for example, make the current IP of one of the problem stations "unavailable" and it will DHCP NAK the lease and when it gets a new IP, the DDNS entry gets updated/created. But that's an UGLY hack and *can't* be the best way, can it?
> So, is there some way to force all DHCPD DDNS records to "update" even if they haven't changed?
> Obviously this will place some [or lots, depending] of additional load on BIND, but that's a given.
> [I'm quite sure my BIND server will handle the load, and if it doesn't - I'll take responsibility for burning down my house, all because I misused the gasoline and matches. :) ]
> Now, perhaps I'm looking at it all wrong, and in my tunnel vision I can't find my way out of a wet paper bag - and if so, please correct me. But I do need some way, if possible, to force creation of the DDNS entries for these clients. 
> "Help, I've fallen and I can't get up!" [I feel about that competent at the moment too!]
> -Greg
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