Installing and Administering Internet Services

Chapter 3 65
Configuring and Administering the BIND Name Service
Overview of the BIND Name Service
round-robin address rotation, the name server rotates the order of the
addresses returned, so connections to rainbow will be balanced among
red, blue, and green.
Round-robin address cycling can also affect multi-homed hosts (hosts
with multiple IP addresses). However, if a multi-homed host belongs to
multiple subnets, the address records will be sorted by the resolver to
favor the addresses to which the querying host is directly connected, or
those that correspond to the networks in the querying host’s sortlist
(specified in /etc/named.boot).
Also note that for multi-homed hosts with multiple interfaces attached to
the same subnet, no load sharing is done for outbound traffic. The
transport software will select an interface for outbound traffic according
to the target IP address and use that interface consistently, regardless of
the interfaces on which it is receiving inbound traffic from the target IP
address.
Round-robin address cycling is enabled by default. However, with BIND
4.9.3, if you do not want to use this feature, you can disable it by adding
the following entry to the named boot file, /etc/named.boot:
options no-round-robin.
How BIND Resolves Host Names
Because complete domain names can be cumbersome to type, BIND
allows you to type host names that are not fully qualified (that is, that do
not contain every label from the host to the root and end with a dot). This
section describes how the name server resolves host names.
NOTE It is always correct to use a name that contains all of the labels from the
host to the root and does not end with a dot. Names that end in a dot are
not allowed in the following places: mail addresses, the hostname
command, and network-related configuration files. Names that contain
all of the name components and end in a dot are used with commands
like nslookup, ping, and telnet, to facilitate the lookup process.
• If the input host name ends with a dot, BIND looks it up as is,
without appending any domains to it.