BIND Configuration File Guide--server Statement

server ip_addr {
  [ edns yes_or_no; ]
  [ bogus yes_or_no; ]
  [ support-ixfr yes_or_no; ]
  [ transfers number; ]
  [ transfer-format ( one-answer | many-answers ); ]
  [ keys { key_id [key_id ... ] }; ]
};

The server statement defines the characteristics to be associated with a remote name server.

If you discover that a server does not support EDNS you can prevent named making EDNS queries to it by specifying edns no;. The default value of edns is yes.

If you discover that a server is giving out bad data, marking it as bogus will prevent further queries to it. The default value of bogus is no. Marking a server as bogus will mark all other addresses for that server as bogus when a match is made when looking up a server's address by name.

If the server supports IXFR you can tell named to attempt to perform a IXFR style zone transfer by specifing support-ixfr yes. The default value of support-ixfr is no.

The server supports two zone transfer methods. The first, one-answer, uses one DNS message per resource record transferred. many-answers packs as many resource records as possible into a message. many-answers is more efficient, but is only known to be understood by BIND 8.1 and patched versions of BIND 4.9.5. You can specify which method to use for a server with the transfer-format option. If transfer-format is not specified, the transfer-format specified by the options statement will be used.

The transfers will be used in a future release of the server to limit the number of concurrent in-bound zone transfers from the specified server. It is checked for syntax but is otherwise ignored.

The keys clause is used to identify a key_id defined by the key statement, to be used for transaction security when talking to the remote server. The key statememnt must come before the server statement that references it. When a request is sent to the remote server, a request signature will be generated using the key specified here and appended to the message. A request originating from the remote server is not required to be signed by this key.