10.13 Compatibility

Now, to wrap things up, we'll cover some configuration substatements related to your name server's compatibility with resolvers and other name servers.

The rfc2308-type1 substatement controls the format of the negative answers your name server sends. By default, BIND 8 and 9 name servers include only the SOA record in a negative response from a zone. Another legitimate format for that response includes the zone's NS records, too, but some older name servers misinterpret such a response as a referral. If for some odd reason (odd because we can't think of one) you want to send those NS records as well, use:

options {
	rfc2308-type1 yes;
};

rfc2308-type1 is first supported in BIND 8.2; BIND 9 doesn't support it.

Older name servers can also cause problems when you send them cachednegative responses. Before the days of negative caching, all negative responses were, naturally, authoritative. But some name server implementors added a check to their servers: they'd accept only authoritative negative responses. Then, with the advent of negative caching, negative responses could be nonauthoritative. Oops!

The auth-nxdomain options substatement lets your name server falsely claim that a negative answer from its cache is actually authoritative, just so one of these older name servers will believe it. By default, BIND 8 name servers have auth-nxdomain on (set to yes); BIND 9 name servers turn it off by default.

Finally, when some adventurous souls ported BIND 8.2.2 to Windows NT, they found they needed the name server to treat a carriage return and a newline at the end of a line (Windows' end-of-line sequence) the same way it treated just a newline (Unix's end-of-line). For that behavior, use:

options {
	treat-cr-as-space yes;
};

BIND 9 ignores this option because it always treats carriage return and newline and a newline alone the same way.