Rather than adding the overhead of managing secondary DNS zones you may want
to look at other options. Generally speaking, you'd opt for AD Integrated
zones rather than a Primary/ Secondary relationship in you AD Domain making
external secondaries a less than attractive option.
Generally, you would use simply make the other servers aware of the
additional DNS servers through network properties or forwarders. (Pros and
Cons with each.) This lets you protect your domain from any problems in the
foreign DNS and allows you to use AD Integrated DNS as well.
MCSE, MCTS: SQL 2005, Project+
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