Technical data

Configuring and Managing BIND
5.3 Configuring the BIND Server (BIND 8.1)
Table 5–4 (Cont.) Boolean Options
Option Description
multiple-cnames If yes, then multiple CNAME resource records allow for a
domain name. The default is no. Allowing multiple CNAME
records is against standards and is not recommended. Multiple
CNAME support is available because previous versions of
BIND allowed multiple CNAME records, and these records
have been used for load balancing by a number of sites.
notify If yes (the default), DNS NOTIFY messages are sent when a
zone for which the server is authoritative changes. The use
of NOTIFY speeds convergence between the master and its
slaves. Slave servers that receive a NOTIFY message and
understand it contact the master server for the zone to see if
they need to do a zone transfer; if they do, the servers initiate
the zone transfer immediately. The
notify option can also be
specified in the zone statement, in which case it overrides the
options
notify statement.
recursion If yes, and a DNS query requests recursion, then the server
attempts to do all the work required to answer the query. If
recursion is not on, the server returns a referral to the client
if it doesn’t know the answer. The default is yes. See also
fetch-glue above.
Example 5–2 shows how to specify Boolean options in an options statement.
Example 5–2 Boolean Options
options {
auth-nxdomain yes;
deallocate-on-exit no;
fake-iquery no;
fetch-glue yes;
host-statistics no;
multiple-cnames no;
notify yes;
recursion yes;
};
5.3.2.3 Forwarding
You can use the forwarding facility to create a large sitewide cache on a few
servers, reducing traffic over links to external name servers. You can also use the
forwarding facility to allow queries by servers that do not have direct access to
the Internet, but wish to look up exterior names anyway. Forwarding occurs on
only those queries for which the server is not authoritative and does not have the
answer in its cache. Table 5–5 lists the forwarding options.
Configuring and Managing BIND 5–13