Article ID: 818020 - View products that this article applies to.
When you use DNS Manager or the dnscmd command to delete the last root hint from a Microsoft DNS server, one or more of the deleted root hints may reappear after about 15 minutes. You do not receive a warning that the root hints are not deleted permanently.
Note Microsoft does not support the removal of all root hints from a Microsoft DNS server. A Microsoft DNS server must have at least one root hint. However, you can replace the existing root hints with new root hints. When you replace root hints, the change is permanent, and the old root hints do not reappear. If the DNS server if forwarding, click to select the Do not use recursion for this domain check box on the Forwarders tab in DNS Manager to make sure that the root hints will not be used.
The root hints can be removed permanently and completely by removing the root hints from the DNS Manager, the CACHE.DNS file and from Active Directory. The root hints come back in this scenario is because the root hints still exist in the other two locations (CACHE.DNS file and Active Directory).
When a DNS server is not a root server, you must specify root hints in the form of at least one name server (NS) resource record, and you must indicate a root DNS server and a corresponding host (A) resource record for that root DNS server. Otherwise, the DNS server cannot contact the root DNS server on startup and cannot answer queries for names outside its own authoritative zones.
Root hints are a list of the DNS servers on the Internet that your DNS servers can use to resolve queries for names that it does not know. When a DNS server cannot resolve a name query by using its local data, it uses its root hints to send the query to a DNS server. DNS servers that try to locate and to find other DNS servers must have these hints.
To update root hints on the DNS server, follow these steps:
Article ID: 818020 - Last Review: December 3, 2007 - Revision: 6.4
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