Configuring a Caching-Only Server
Caching-only servers are used to speed up query response by collecting a large number of cached records in response to client lookups. A caching-only server does not have a copy of a zone file and is therefore not authoritative. It obtains resource records from other DNS servers on behalf of clients.
The name cache is kept in memory, so make sure that the machine has lots of RAM. You can see the amount of memory used by DNS via the Task Manager window. Select the Processes tab and look for dns.exe. Get a baseline value then see how much it goes up as time goes by.
If you want to flush the cache, you can stop and start the DNS service or use the DNSCMD utility. The syntax is dnscmd /clearcache. Purging defeats the purpose of a caching-only server, however; so if you find yourself purging frequently to maintain performance, consider getting more memory.
A caching-only server does not pull zone transfers, so there is no need to add it to the list of secondaries at the master DNS server.
The initial DNS service installation is the same as for a primary DNS server. Only the configuration steps differ (see Procedure 5.16). Load the service drivers using the steps in "Installing and Configuring DNS Servers," earlier in this chapter, and then return here to configure the service.
Procedure 5.16 Configuring a Caching-Only Server
Open the DNS console.
Right-click the server icon and select PROPERTIES from the flyout menu. The Properties window opens.
Select the Root Hints tab.
Delete the TLD root servers from the list (if they are there) using the Remove button.
Click Add. The New Resource Record window opens with the Name Server (NS) tab showing.
Enter the FQDN of the master name server and its IP address. Click Add to add the IP address to the list. You can configure multiple name servers. They do not need to be in the same zone.
Click OK to save the entries and return to the Properties window.
Click OK to save the list and return to the DNS console.
Close the console.
Verify that the caching-only server works by pinging a remote server name from a client that is configured to use the server for DNS. Ping several host names to stock up the cache and then try the same names from another desktop. The response time should be much quicker.