Conditional forwarding was first introduced in Windows Server 2003 by Microsoft. It speed up the DNS query requests if used properly. It accepts the name resolution request for a specific domain. For example, DNS Server can be configured to forward any request for microsoft.com domain only to a specific name server which is authoritative for that domain.
1. Client sends a query to the DNS server for resolving www.microsoft.com into its address.
2. DNS Server accepts the request and checks its local DNS database for its associated address. If it does not find the IP address of www.microsoft.com in its cache, it will check the list of forwarders .
3. On that list, it will find conditional forwarding enabled for that domain and will forward the resolution request to that IP address which is authoritative for the www.microsoft.com domain.
4. The Microsoft.com name server will immediately resolve the www.microsoft.com name to its IP address without contacting the root DNS servers and will send the same information to that DNS server.
5. DNS server will forward that information to the client and client will be connected to the www.microsoft.com site.
How to configure Conditional Forwarding
1. To configure Conditional forwarding, first we need to know the IP address of authoritative server responsible for resolving that particular domain. To do so, run the nslookup command or you may use lots of web sites providing detail records about any domain, such as http://www.whois.net and others.
2. Once we came to know the IP address of authoritative server, open the DNS Server Properties from DNS Management snap-in. Then click Forwarders >Enter the domain name, Microsoft.com and the IP address, like shown below.
