Active Directory integrated DNS zone - client registration process.

I'm in the process of planning for an NT to Active Directory migration for an environment that is approx. 3000 users, 3000 workstations, and 350 servers.  I'm working on planning my DNS infrastructure at the moment.  Initially we are planning on having 4 domain controllers that will also serve as our AD-integrated DNS servers in the DHCP scope.  We will remove the root-hints from these four machines and set them up to forward to a pair of caching DNS servers that will then forward out to our ISP's servers.  My question is, when a client machine or member server starts up and registers itself in DNS, will it always try to register with the first DNS server in it's TCP/IP properties/DHCP assignment, or does it pick one of its DNS servers at random?  I'm concerned because if this is the case, then that one DNS server/Domain Controller that is first in the DHCP scope will be getting slammed first thing in the morning with all of the authentication requests and DNS registrations that it will be receiving.  Any suggestions are appreciated.  Thanks in advance.
cdavidson0724Asked:
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mvvinodCommented:
First of all some basics here....

Rule 1: DHCP only updates PTR records in the DNS Zone. Clients always update their host names. This is by design. DNS client service does this job...

2. All clients always register to first DNS servers only. If first server is not available, it uses the second....

3. You can run DNS on any box other than DC. In those boxes you should configure DNS server as secondary and configure zone transfer between primary and secondary... I dont receommend this way since troubleshooting is a lot easier in only AD integrated zones.

CLUSTERING is a good option. But in my opinion for DHCP, it is a waste of money. USELESS

looking at the number of clients, looks like you are going to have several routed subnet. If you are thinking about single bradcast network, forget it. IT WILL NOT WORK FOR 3000 clients...

Having said , we are having several subnets, allocate 1 DHCP server for every 3/4 subnet and use DNS1 as primary in that scope....
In the next 3/4 subnet, allocate DNS2 as primary in that subnet...

By doing this, you are reducing the number of clients that depend on 1 dhcp/dns server thereby automatically load balancing both....

Let me know if you have more questions...

Vinod.
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mcsweenSr. Network AdministratorCommented:
Since you have so many workstations that will be starting up at the same time you should look at creating a DHCP cluster.  Configure the DHCP server to do the dynamic updates instead of having the clients do it themselves (much more reliable).  I would also install DNS on the DHCP servers, this way they should update the DNS records on themselves then replication will take care of the rest.
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cdavidson0724Author Commented:
Good point and I would consider that, but currently our Network Management team runs DHCP from Cisco Network Registrar, so our side of the house has no control over DHCP.  

Any ideas on how client machines and servers choose which DNS server to register with?
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mcsweenSr. Network AdministratorCommented:
I'm pretty sure they are going to hit the first server on the list.  And since you are assigning IP addresses via DHCP it's going to be the same server.  

I guess since Cisco is handling DHCP your best bet would be to setup a "Server Cluster" for DNS.  You will assign a virtual IP to the cluster, make that the first DNS address that's handed out by DHCP.
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cdavidson0724Author Commented:
Wouldn't that require me to cluster my domain controllers since DNS will live on the same boxes?
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mcsweenSr. Network AdministratorCommented:
You can run DNS on a box that's not a DC.
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cdavidson0724Author Commented:
I thought that AD-integrated DNS zones had to live on DCs.
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mcsweenSr. Network AdministratorCommented:
I apologize, you are correct...Integrated DNS zones do have to reside on a DC.  You will have to make each of these "cluster dns" servers a DC as well.
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cdavidson0724Author Commented:
I'm not entirely sure that you can or would want to cluster a domain controller.
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cdavidson0724Author Commented:
Thanks mvvinod...point taken
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mvvinodCommented:
You are welcome ! Glad to help.
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