Configuring a DNS Server to Use a Forwarder
A DNS server can be configured to send an out-of-zone query to another on the chance that the server has already located the record and has it in cache. If the bet fails and the record is not available, the forwarding server walks the tree to find the record on its own.
Before configuring a server to send queries to a forwarder, it is considered good manners to inform the administrator. A forwarding server has the potential for sending many thousands of queries to the forwarder.
The example steps assume that you are configuring an existing DNS server inside a firewall and using a forwarder outside the firewall to resolve Internet addresses. Configure the forwarding option as shown in Procedure 5.17.
Procedure 5.17 Configuring a DNS Server to Use a Forwarder
Open the DNS console.
Right-click the server name and select PROPERTIES from the flyout menu. The Properties window opens.
Select the Forwarders tab.
Select the Enable Forwarders option.
Enter the IP address of the forwarder and click Add to add it to the list.
Leave the Forward Time-Out (seconds) option set for five seconds. The forwarder should answer out of its cache, which doesn't take very long. If the forwarder takes longer than five seconds to respond, it is probably doing a search.
Click OK to save the settings and return to the DNS console.
Stop and start the DNS service by right-clicking the server icon and selecting ALL TASKS | RESTART from the flyout menu.
Verify that the forwarder works by pinging an Internet host name from a DNS client. The ping succeeds after a short time delay. If the ping does not succeed, check the IP addresses to make sure that you are pointed at the correct server.