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AD, DNS and Windows 2003/2008

My configuration

3 DC
DC1 = Windows 2008 R2, DNS, GC, all 5 FMSO roles, IP = 126.0.0.9, DNS1= 126.0.0.9, DNS2= 126.0.0.10
DC2 = Windows 2003 SP2, Exchange, DNS, GC, IP= 126.0.0.105, DNS1 = 126.0.0.10, DNS2 = empty
DC3 = Windows 2003 SP2, DNS, GC, IP = 126.0.0.10, DNS1 = 126.0.0.10, DNS2 = 126.0.0.9

Is this DNS configuration OK?
What is the recommended DNS configuration in TCP/IP properties of each DC?

(I had a problem this morning that when I started DC1 alone (DC2 and DC3 where offline) DNS service would not start. When DC2, DC3 went online some minutes after, everything when back to normal, and DNS service started sucessfully,  that is the reason I prefer to check DNS configuration)

Thank you
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gadsad
Asked:
gadsad
1 Solution
 
Krzysztof PytkoActive Directory EngineerCommented:
Try to configure it this way

DC1: Primary DNS of DC2, Secondary DNS of itself, Tertiary DNS of 127.0.0.1 (loopback interface)
DC2: Primary DNS of DC3, Secondary DNS of DC1, Tertiary DNS of 127.0.0.1 (loopback interface)
DC3: Primary DNS of DC1, Secondary DNS of DC2or3, Tertiary DNS of 127.0.0.1 (loopback interface)

This should prevent of "DNS island" which probably took place in your environment. DNS service couldn't start and there was problem with AD startup.

More about DNS island at
http://support.microsoft.com/kb/275278

Regards,
Krzysztof
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Lester_ClaytonCommented:
The Microsoft recommended configuration is to set the Alternate DNS server for Domain Controllers to be 127.0.0.1 - only if they are running DNS services though.

Unfortunately, you've not told us what your DC IP addresses are, so I could not give you a recommended configuration.

I have 2 domain controllers in each of my forests, and I make the 2 Domain Controllers point to their own IP and the other Domain Controller's IP for DNS.

In a 3 Domain Controller environment, I'd make them still talk to their own IP as the first DNS entry, and then flip a coin to see which other domain controller/DNS server gets the second one :D
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Krzysztof PytkoActive Directory EngineerCommented:
They told us :) Read question once again ;)

Krzsztof
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Lester_ClaytonCommented:
I got confused with all the IP's :)
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Darius GhassemCommented:
Also, best practices not to use 127.0.0.1 you should use the actual IP addresses. Loopback addresses themselves can cause DNS issues in multiple DNS server environment.
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Krzysztof PytkoActive Directory EngineerCommented:
Hi,

today I was reviewing posts on EE and I found one interesting post, where Mike (mkline71) posted a link to Ask DS Team blog. There where similar question about best DNS practices. I read that article and I think it's worth placing it here for you :) In my opinion you will find all answers for your questions ;)

http://blogs.technet.com/b/askds/archive/2010/07/17/friday-mail-sack-saturday-edition.aspx#dnsbest

Krzysztof
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gadsadAuthor Commented:
thank you
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