ddns updates when using failover?

Nicolas C. dhcp at nryc.fr
Tue Jan 14 21:00:47 UTC 2014

On 14/01/2014 17:07, John Miller wrote:
> Hello folks,
> I'm digging into how ISC dhcpd (we're running 4.2.4-P2) handles dynamic
> updates when acting as part of a failover pair.  Thus far, I'm seeing
> _both_ servers in the failover pair send ddns updates when a new lease
> is generated, rather than only the server sending the DHCPACK.  Is this
> normal behavior?

I don't think so, in failover mode both server reply but in the end only 
one gives the lease and do the DDNS update.

Can you give us some of your logs ?

Be careful with DDNS and failover : when a server dies and the other 
goes into "partner down", it works, but when the "dead" server comes 
back, it will purge all the expired leases it was managing.

So basically a DHCP back from "partner down" mode after the lease time 
will do a *massive* cleanup in the DNS, even if the leases were 
correctly handled by the other DHCP.


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