[dns-operations] Client retry behavour?

Simon Lyall simon at darkmere.gen.nz
Wed May 9 10:25:08 UTC 2007

I was worrying about my recursive name servers today and it occurred to me
that I wasn't sure what the behaviour of clients was when the primary name
server started getting flaky. The driver behind this was did I need to
make the primary extremely reliable or would clients ( most home users)
just use the secondary (and tertiary) name servers OK?

Having a primary recursive server that is 3-4 9's available and a
secondary that is (independently) 3-4 9's available is easier than making
sure the primary that is 5+ 9's available.

Anyway looking around I found this page on Microsoft's site:


( click on "DNS Processes and Interactions" and scroll down a couple of
pages till you get the section between the 3rd flowchart and the blue

Which tells me how Windows Server 2003 works and I think applies to other
Windows versions.

My questions are:

1. Does this actually apply to desktop Windows 98, 2000, 2003, XP and

2. What does this mean in practice:

"The DNS Client service keeps track of which servers answer name queries
more quickly, and it moves servers up or down on the list based on how
quickly they reply to name queries. "

3. Does anyone have a similar overview for MacOS X and Desktop Linux?

and the nitty gritty questions is:

4. If my primary starts ignoring 5%, 20%, 50% or 100% of queries what
will be the impact on my end users if I have a secondary server available
this is answering perfectly?

Anyway have any pointers? It sounds like the sort of thing people would
test (  Or Nominum would have a white paper on )  but I couldn't see

Simon J. Lyall  |  Very Busy  |  Web: http://www.darkmere.gen.nz/
"To stay awake all night adds a day to your life" - Stilgar | eMT.

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