[nsd-users] Question about response source address and dynamic interfaces

Gavin Brown gavin.brown at centralnic.com
Thu Aug 16 14:39:57 UTC 2012

Hi there,

I have a FreeBSD box (hostA) running NSD. It has a management address
( and a service address ( It is part of a clustered
pair with a Linux machine (hostB) that has a management address
( and a service address ( DNS queries are sent to the
two service addresses. Heartbeat is used to co-ordinate the pairs: if
hostB goes offline, then the service address ( is brought up on
hostA so that it can answer queries, and vice versa.

The problem is this: without an ip-address entry in nsd.conf, responses
are sent from the management address ( since that is the
"primary" interface of the host. I can fix this during normal operations
by adding an ip-address entry for

However, during failover, queries sent to will be answered with
the wrong source address. Again, I could fix this using an ip-address entry.

But - when the machine boots, this IP address isn't assigned to hostA,
so if it appears in nsd.conf, NSD will refuse to start. BIND (which I'm
using on hostB) doesn't have this problem.

Has anyone else solved this problem? Or do I need to write scripts to
munge nsd.conf and restart it during failover/failback?


Gavin Brown
Chief Technology Officer
CentralNic Ltd
Innovative, Reliable and Flexible Registry Services
for ccTLD, gTLD and private domain name registries

CentralNic Ltd is a company registered in England and Wales with company
number 4985780. Registered Offices: 35-39 Moorgate, London, EC2R 6AR.

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