Bind 9 Administrator Reference Manual

Chapter 6. BIND 9 Conﬁguration Reference

mail.example.net will be provided as well, if known. Setting these options to no disables this

behavior.

These options are intended for use in authoritative-only servers, or in authoritative-only views.

Attempts to set them to no without also specifying recursion no; will cause the server to ignore the

options and log a warning message.

Specifying additional-from-cache no actually disables the use of the cache not only for additional

data lookups but also when looking up the answer. This is usually the desired behavior in an

authoritative-only server where the correctness of the cached data is an issue.

When a name server is non-recursively queried for a name that is not below the apex of any served

zone, it normally answers with an "upwards referral" to the root servers or the servers of some other

known parent of the query name. Since the data in an upwards referral comes from the cache, the

server will not be able to provide upwards referrals when additional-from-cache no has been

speciﬁed. Instead, it will respond to such queries with REFUSED. This should not cause any

problems since upwards referrals are not required for the resolution process.

match-mapped-addresses

If yes, then an IPv4-mapped IPv6 address will match any address match list entries that match the

corresponding IPv4 address. Enabling this option is sometimes useful on IPv6-enabled Linux

systems, to work around a kernel quirk that causes IPv4 TCP connections such as zone transfers to

be accepted on an IPv6 socket using mapped addresses, causing address match lists designed for

IPv4 to fail to match. The use of this option for any other purpose is discouraged.

6.2.14.2. Forwarding

The forwarding facility can be used to create a large site-wide cache on a few servers, reducing trafﬁc

over links to external nameservers. It can also be used to allow queries by servers that do not have direct

access to the Internet, but wish to look up exterior names anyway. Forwarding occurs only on those

queries for which the server is not authoritative and does not have the answer in its cache.

forward

This option is only meaningful if the forwarders list is not empty. A value of first, the default,

causes the server to query the forwarders ﬁrst, and if that doesn’t answer the question the server will

then look for the answer itself. If only is speciﬁed, the server will only query the forwarders.

forwarders

Speciﬁes the IP addresses to be used for forwarding. The default is the empty list (no forwarding).