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IT Interview Questions:Describe a few methods of finding an MX record for a remote domain on the Internet. What does "Disable Recursion" in DNS mean?
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(Continued from previous question...)
IT Interview Questions:Describe a few methods of finding an MX record for a
remote domain on the Internet. What does "Disable Recursion" in DNS mean?
In the Windows 2000/2003 DNS console (dnsmgmt.msc), under a server's
Properties -> Forwarders tab is the setting
Do not use recursion for this domain
. On the Advanced tab you will find the confusingly similar option
Disable recursion (also disables forwarders)
. Recursion refers to the action
of a DNS server querying additional DNS servers (e.g. local ISP DNS or the
root DNS servers) to resolve queries that it cannot resolve from its own
database. So what is the difference between these settings? The DNS server
will attempt to resolve the name locally, then will forward requests to any
DNS servers specified as forwarders. If Do not use recursion for this domain
is enabled, the DNS server will pass the query on to forwarders, but will not
recursively query any other DNS servers (e.g. external DNS servers) if the
forwarders cannot resolve the query. If Disable recursion (also disables
forwarders) is set, the server will attempt to resolve a query from its own
database only
. It will not query any additional servers. If neither of these
options is set, the server will attempt to resolve queries normally: ... the
local database is queried ... if an entry is not found, the request is passed
to any forwarders that are set ... if no forwarders are set, the server will
query servers on the Root Hints tab to resolve queries beginning at the root
domains.
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