Adding to the Notify list is how you enable access. This can be applied to each zone. NS2 the secondary and normally will be making most of the queries to the Internet. A, B, C and D will forward to NS1, then NS2, then other backup servers. Determines port on which server sends UDP queries to other DNS servers.
Administrators can easily identify, monitor and control forwarding queries.
Determines whether server attempts to clean up responses to avoid cache pollution. Limits number of A records put in answer to query. Administrators can reduce logging to avoid DoS because of log entries. Administrators can log to the packet level if needed. Administrators can control a specific servers behavior.