forwarders are unreachable -> lookup fails?

[Jim Reid]

>>>>> "Brad" == Brad Knowles <brad.knowles at skynet.be> writes:

    Brad> 	The moral to this story is that you want to make
    Brad> absolutely, positively, certain that the servers you are
    Brad> forwarding queries to are always up and operational.
    Brad> Otherwise, you shouldn't be forwarding queries to them.

Another moral is don't forward if at all possible. Forwarding is evil.
Unfortunately it is a necessary evil in some circumstances. Using
forwarding to build up a huge cache on one central name server is not
a valid justification for forwarding in my opinion.

    Brad> 	That said, I believe that BINDv9 is more intelligent
    Brad> about detecting and remembering when forwarding servers are
    Brad> down/slow (using the same algorithms formerly used to
    Brad> determine how fast various remote nameservers are for
    Brad> various zones, such as the root and TLD zones)

Correct. The same thing is done in 8.2.3 too. From the CHANGES file:

 997.   [support]       forwarders are now used in order by measured RTT.