DNS using remote branch office server

Is the Office 2008 machine a domain member server?? And is your DNS server AD integrated??
You can give it a shot and try to install a local DNS server on the Server 2008 machine, point your local clients to this machine using DHCP and add conditional forwarders for your own domain pointing to the main Office 2003 domain servers. Tbh i would say upgrading the 2008 server to a DC, this way you will make your life much easier...

Why will you not be making the server in the branch office a Domain Controller? It is best practice to have AT LEAST one Domain Controller at a remote location, and ALL DCs should be Global Catalogs (GCs). This means authentication traffic can remain LOCAL to the site, reducing the traffic required to flow over the VPN link to the DCs in the main site. Furthermore, a local DC means the site can continue to operate if the VPN line or Internet connection is lost, since a writable copy of the Active Directory database is held locally.

If you are concerned about DC security, you should consider deploying a Windows Server 2008 Read-Only Domain Controller (RODC) to the remote site. This will give similar benefits (local authentication), but does not hold a writable copy of Active Directory, so your domain cannot be damaged as easily if someone gains physical access to the server.

Having a server act as a DC is by no means a resource intensive task, and any modern server is capable of doing so. Having a local DC means it can become a DNS server, with zones replicating using AD-integrated zones, and then forwarders configured to forward non-local DNS requests directly to the nameservers at the ISP.

-Matt

I haven't tried installing a 2008 DC in a 2003 environment.
Can Windows 2003 and 2008 DCs hapily coexist?

Windows 2003 and 2008 DCs will happily co-exist. I have several networks running in this configuration and have not experienced any issues.

You need to remember that you cannot install a 2008 DC until the schema has been extended. This is a routine operation, which simply entails loading the Server 2008 DVD into your current Schema Master DC. Then, open a Command Prompt, switch to x:\SOURCES\ADPREP (where x: is the DVD drive) and run

adprep /forestprep
adprep /domainprep /gpprep

That will prepare the domain and the schema to support 2008 DCs, at which point you can then promote the 2008 DC as a DC via the standard dcpromo procedure.

-Matt

How do clients query for domain servers?  The reason I ask is the following:

If I have the DC running in the branch office - likely on the same subnet as the clients, at least for now - when I boot a Windows XP client machine, will it broadcast it's DC request on it's local subnet first, and the local DC will reply?

I don't entirely understand how clients discover the DC.  If I put a local DC in the branch office, I want to make sure that the clients are querying it correctly, rather than going to the vpn to query our main office DCs.

"If I have the DC running in the branch office - likely on the same subnet as the clients, at least for now - when I boot a Windows XP client machine, will it broadcast it's DC request on it's local subnet first, and the local DC will reply?"

Yes they do, they first look at their own site and broadcast a request to the network for receiving an ip address.. After that, when it also receives a DNS server ip address it will ask that DNS server for it's SRV record, this is the DC the machine will authenticate against, at least it will find the closest server in range..

Setup domain site...worked.  :)