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We currently run a 2003r2 server and are looking at adding a cloud server to aid with redundancy.

It's current roles are: file server print server IIS server SQL server domain controller DNS server DHCP server AD server

So that the local terminals can access the net and therefore the cloud server if the local server is down we want to move DHCP and DNS services to the router but are unsure if this is possible or what impact it will have on the other server roles.

Any thoughts would be appreciated.

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3 Answers 3

DNS

Windows servers acting as Active Directory domain controllers will populate their internal DNS configuration with a lot of interesting service records that are invisible during normal operation. These records allow the member servers and client workstations joined to the domain to participate in the domain without a lot of extra configuration (for instance, this is how client workstations can figure out how to join the domain just from its name without needing to specify the name of a domain controller).

If the other member servers and client workstations are not configured to use the domain controller for DNS, then they won't be able to find these service records and a lot of automagical configuration just won't work or will be a lot harder to do.

DHCP

It doesn't matter whether the domain controller or the router provides DHCP services.

Solution

Here is what I'd do in your situation.

  1. Set up the router to provide DHCP and DNS services to your network.
  2. Configure DHCP on the router to specify two DNS servers to the clients: FIRST the domain controller, and SECOND the router itself.
  3. Disable DHCP on the domain controller but leave DNS running.

This setup will have the following qualities:

  • DHCP service will be available whether the domain controller is available or not.
  • DNS service will be available whether the domain controller is available or not.
  • During normal operation, the clients will ask the domain controller for DNS queries first, and all of the autoconfiguration stuff will work properly.
  • When the domain controller is offline, the clients will failover to the router for DNS. AD autoconfiguration will not work, but that's immaterial since the domain controller is offline in this scenario.
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no, it's not a requirement that it is dns and dhcp server.

DHCP server is not required (and not wanted in a hosting environment)

DNS server is not required, but you have to make sure that the hosted server is using the internal server as source for it's DNS requests. But of course, this then brings you a single point of failure, so it's simplest to also add the DNS server role to the hosted server too.

The other solution for DNS would to add the required entries manually, but that's pretty advanced stuff.

André

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he didnt mention anywhere this is a hosting server... –  anthonysomerset Aug 23 '11 at 7:17
    
"A cloud server" is for me a server which is hosted somewhere in the internet... –  André Schild Sep 1 '11 at 5:32

to run a domain server on windows you must run a windows dns server, however it is not strictly required to be on the same server as long as it is linked up to the AD server so the AD server can make the neccesary updates to manage your domain

DHCP again is not critical if you statically assign IP's to each machine or if you use say your router to assign dhcp, as long as they have the correct DNS settings to allow your client machines to correctly connect to the server resources in the router it should just work correctly, moving to the router as default will improve your redundancy from the server failing so i'd recommend doing anyway

if your cloud server is running as a slave DC, then it can also run as a slave dns server too without issue, just make sure your dhcp is setup correctly to handle it, you may however want to setup a vpn tunnel between the cloudserver and your local network in order to secure the transmission of data across that channel

but if your not sure its probably simpler and safer for you to leave the dhcp and dns services installed on your AD server

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2  
It's not strictly true that you must run a Windows DNS server to use a Windows machine as a domain controller; it's possible to configure a BIND DNS server to serve the records Active Directory requires. –  Handyman5 Aug 23 '11 at 7:40
    
good point but a dns server is still required, and for simplicity a windows dns server is simplest to operate/integrate :) –  anthonysomerset Aug 23 '11 at 7:42
    
Technically you need a DNS server that supports SRV records –  Matt Aug 23 '11 at 8:21
    
Actually, a DNS server is not strictly required either; it's possible to set up an AD domain that does not publish the SRV records and uses NetBIOS to locate domain controllers. Admittedly, this is a pathological case, but it is possible. –  Handyman5 Aug 23 '11 at 8:44
1  
-1 for saying you need a Windows DNS server. While I would question the sanity of someone who did it any other way without one hell of an edge case reason, it's not actually a requirement. –  RobM Aug 23 '11 at 10:43

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