Root hints are name and address pairs that enable a DNS server to locate root DNS servers. They help resolve DNS queries for hosts in domains for which the server is not an authority. During a new DNS server installation, Windows Server uses the Cache.dns file stored in %systemroot%\System32\DNS to implement root hints.

If you originally set up a DNS server for internal queries only, it's possible that the root hints in your server are empty or that someone has modified them to point to internal servers. If you now want the DNS server to resolve queries for external hosts, it's important to ensure that the server has a valid set of root hints.

To configure root hints for the server, follow these steps:

1. Ensure that you've configured the server to use an upstream DNS server capable of resolving external hosts.

2. Open the DNS console from the Administrative Tools folder.

3. In the left pane, right-click the server in question, and choose Properties.

4. On the Root Hints tab, select the first server in the Name Servers list, and click Edit.

5. Click Resolve to resolve the host name to its IP address, and click OK. You can also manually enter the IP address for the target server.

6. Repeat the process for the remaining root servers, and add others if necessary.

7. When you've finished, close all dialog boxes.