Primary authoritative name servers must be configured to only receive zone transfer requests from specified secondary name servers.

Authoritative name servers (especially primary name servers) must be configured with an allow-transfer access control substatement designating the list of hosts from which zone transfer requests can be accepted. These restrictions address the denial-of-service (DoS) threat and potential exploits from unrestricted dissemination of information about internal resources. Based on the need-to-know, the only name servers that need to refresh their zone files periodically are the secondary name servers. Zone transfer from primary name servers must be restricted to secondary name servers. The zone transfer must be completely disabled in the secondary name servers. The address match list argument for the allow-transfer substatement must consist of IP addresses of secondary name servers and stealth secondary name servers.