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DNS forward lookup zones and multiple DCs: how many host (A) records should there be

Posted on 2008-06-19
Medium Priority
Last Modified: 2011-10-03
I'm using Windows 2003 Server, and I have a question regarding whether each DC should be set up with a Host (A) entry for a website. I have a related question about redundancy.

I have multiple domain controllers: let's call them dc1.contoso.com (, dc2.consoso.com(, , dc3.contoso.com (

I have domain names set up in the forward lookup zones of the DNS. Lets call one of them blabber.com.  
If I click on blabber.com in the foward lookup zome of dc1.contoso.com, this is what I see below the soa record:

(same as parent folder)     Name Server (NS)    dc1.constoso.com.local.
(same as parent folder)     Name Server (NS)    dc2.constoso.com.local.
(same as parent folder)     Name Server (NS)    dc3.constoso.com.local.
(same as parent folder)     Host(A)  [IP of dc1.contoso.com]
www                                 Host(A)
admin                                  Host(A)

Question #1:
For my hypothetical blabber.com domain name, I have the DNS server set up at a domain name provider. You want to specify two nameservers for redudancy. Is it correct or NOT correct to do the following:
a)  change the IP number in the "admin" record forward lookup zone of dc1.contoso.com  to point to a different DC's IP, say, dc2.contoso.com
b) change the domain name provider's reference to "admin.blabber.com" to dc2.contoso.com
If this is not correct please tell me the correct way to enable this redundancy.

Question #2:
Look back at what I see in the Forward Lookup Zone of dc1.contoso.com when I click on the blabber.com domain. Note that I have three DCs, but only one host record in the (same as parent folder)  Host(A) with an IP that corresponds to my first DC:
(same as parent folder)     Host(A)  [IP of dc1.contoso.com]

I am wondering if there should be  (same as parent folder)...Host(A)... records entered for each of the DCs with their distinct IPs.  I am also wondering if the "www" and "admin"  Host(A) records need to be entered for the other DCs. Finally, I am wondering if I do need to enter these IPs, if it they will be replicated automatically to the other DCs appearing in the DNS console.  

These questions may reflect an ignorance of the workings of DNS and whatever you can do to explain what's going on will be helpful. It will also be helpful if you can explain the answer from the standpoint of working with the Windows Server DNS GUI.

Question by:kennethfine
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Author Comment

ID: 21824783
Blah, that hypothetical list should have read:

dc1.contoso.com (, dc2.consoso.com(, , dc3.contoso.com (

(same as parent folder)     Name Server (NS)    dc1.constoso.com.local.
(same as parent folder)     Name Server (NS)    dc2.constoso.com.local.
(same as parent folder)     Name Server (NS)    dc3.constoso.com.local.
(same as parent folder)     Host(A)  [IP of dc1.contoso.com]
www                                 Host(A)
admin                                  Host(A)
LVL 31

Accepted Solution

Henrik Johansson earned 2000 total points
ID: 21825240
For the "(same as parent folder)" you should have an A-record for each DC to get redudance for DFS-access.
For redudance for logons, you nead to duplicate the SRV-records (_ldap, _gc, _kpasswd, _kerberos) in the AD-subdomains (_msdcs, _tcp and _udp, _sites) to point on each server. This is done automatically if it's the DNS-zone for the AD-domain and it allows dynamic updates.

www neads to point on all hosts (one A-record for each IP) you expect to answer on requests for www.blabber.com to get redudance. The same thing for admin.

The changes made in DNS-zone will replicate to other DNS servers authoritative for the domain if they have the zone configured as secondary or AD-integrated.

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