DDNS Updates fail When More Than 15 Authoritative Servers (NS records) are listed in a Dynamically Updated Zone

Christopher Cain chris at christophercain.ca
Mon Sep 20 21:30:14 UTC 2010

[I apologize in advance if this is a double post.  I'm not sure if my
original went through]

I was implementing ISC Bind 9.5 at a client site last month and had a single
zone that accepted DDNS updates only from the ISC DHCP service.

The environment consisted of a Master BIND server and almost 25 Windows
slave servers.  All DNS servers were listed as authoritative at first.  This
caused DDNS updates from DHCP to fail with the following message:

"Unable to add forward map from host.domain.com to DNS format

After spending quite a bit of time troubleshooting this issue with no luck,
I was finally successful with DDNS updates after I reduced the number of
authoritative servers for the dynamic zone to 15.  Since I have done this,
the issue has not resurface.

Can anyone help explain to me why this happened and if there is anything I
can do to avoid this from happening in the future?


Christopher Cain
E: chris at christophercain.ca
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