Sequence with multiple forwarders

[Simon Waters]

Jack Aubert wrote:
> 
> My initial
> supposition was that my DNS forwards to both places and passes back the
> first answer that comes in. But that raises some further questions:  If the
> first forwarder were to return with an nxdomain or a servfail message would
> my own DNS wait for the second response at all?

The exact behaviour depends on the version of BIND or other DNS
server in use. BIND 8 queries forwarders pretty much as it would
handle a list of delegated nameservers for the same domain,
prefering the faster server, BIND 9 queries forwarders in order
which can be slow if a DNS server is down.

Since all forwarders will return the same answer if you have
designed your DNS correctly if one returns a NXDOMAIN, then the
domain does not exist, and there is no need to wait for a second
server to return NXDOMAIN also. If a forwarder fails then other
forwarders (if defined) will be asked.