Hub and spoke network with one server location--how to configure DNS?

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http://serverfault.com – I have a hub-and-spoke network with a central office with the servers at one location, and several smaller offices (with no servers) at other locations. Each location has a sonicwall firewall device. Each spoke is connected to the central hub using a VPN tunnel in the firewall. All the computers use active directory logins to the central windows server 2008 domain servers. DNS address lists for each workstation list the primary server first, secondary server second, and two addresses for OpenDNS. The two servers have DNS services running, and DNS forwarders to the OpenDNS servers. (HowTos)