Configuring the new fourth Caching-only DNS server
Although all Domain Name System (DNS) servers cache queries that they have resolved, caching-only servers have only one function: they perform queries, cache the answers, and return the results. Caching-only DNS servers are not authoritative for any domains, and the information that they contain is limited to what they cache while they resolve queries.
Diagram/Explanation to illustrate Caching-only DNS
A caching-only DNS server can be useful at a site where DNS functionality is needed locally but it is not desirable—from the administrative perspective—to create a separate domain or zone for that location, such as a branch office. Query-resolution information is obtained over time from other servers as client requests are serviced.
Connecting to the DNS-CACHE server from the DNS manager
Consequently, the peak network traffic between the caching-only server and other DNS servers occurs when the caching-only server is first put into service. However, if you are dealing with a slow-speed, wide area network (WAN) link between sites, this option might be ideal.
Setting up new IP addresses in the forwarders tab
DNS forwarding is the services that you should resort to if you need to speed up the DNS name resolution process. It is very useful in cases when a request for a domain name is sent by the user but the DNS server, responsible for converting the name into its corresponding IP address, can't locate the matching IP address in its cache and its zones of authority. Via the forward-DNS-resolution-request functionality the queries for a specific non-resolvable address can be directed to alternative name servers.