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Rather than having a DNS server forward all queries it cannot resolve to forwarders, the DNS server can forward queries for different domain names to different DNS servers according to the specific domain names that are contained in the queries. Forwarding according to these domain-name conditions improves conventional forwarding by adding a second condition to the forwarding process.A conditional forwarder setting consists of a domain name and the IP address of one or more DNS servers. To configure a DNS server for conditional forwarding, a list of domain names is set up on the Windows Server2003-based DNS server along with the DNS server IP address. When a DNS client or server performs a query operation against a Windows Server2003-based DNS server that is configured for forwarding, the DNS server looks to see if the query can be resolved by using its own zone data or the zone data that is stored in its cache, and then, if the DNS server is configured to forward for the domain name that is designated in the query (a match), the query is forwarded to the IP address of a DNS Server that is associated with the domain name. If the DNS server has no domain name listed for the name that is designated in the query, it attempts to resolve the query by using standard recursion.
