Using forwarders

Brian Feeny bfeeny at
Wed Jun 25 00:14:56 UTC 2008

I am familiar with using forwarders for conditional forwarding of certain
zones, and understand the reasons for doing so.  I am also familiar with
using forwarders with an internal and external dns model, where you do not
wish to allow your internal dns direct access to external


What about the situation where a company has a single DNS server, that has
direct internet access, and they add a forwarder to their ISP.  What is the
case for this?  I do not believe that DNS processing is so cpu intensive
that pawning off the recursive lookups to another server buys you a whole
lot.  Same goes for bandwidth.  Assume the server has internet access via
NAT or PAT, I don't see any real driving reasons.  I bring this up because I
have a client doing just this, and I cannot think of any reason they do it
like this, they cannot defend why its like this, but their change order
process is so involved that for them to switch it requires more
justification.  I don't like it as well because it introduces a point of
failure that need not be.  Sure the DNS server should locally attempt
recursive lookups on its own if the forwarder times out, but the current
timeout was set so high (5 seconds) that requests were timing out, at least
most of the time, before the queries could be locally resolved.


So can anyone think of practical reasons why one would want to set
forwarders to their ISP?  I mean, even pooling to a much larger DNS cache
(The ISP) doesn't seem like a big win.  





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