Bind 9 Administrator Reference Manual

Chapter 6. BIND 9 Configuration Reference
6.2.22. zone Statement Definition and Usage
6.2.22.1. Zone Types
master The server has a master copy of the data for the zone and will be able to
provide authoritative answers for it.
slave A slave zone is a replica of a master zone. The masters list specifies one
or more IP addresses of master servers that the slave contacts to update
its copy of the zone. By default, transfers are made from port 53 on the
servers; this can be changed for all servers by specifying a port number
before the list of IP addresses, or on a per-server basis after the IP
address. Authentication to the master can also be done with per-server
TSIG keys. If a file is specified, then the replica will be written to this
file whenever the zone is changed, and reloaded from this file on a
server restart. Use of a file is recommended, since it often speeds server
start-up and eliminates a needless waste of bandwidth. Note that for
large numbers (in the tens or hundreds of thousands) of zones per
server, it is best to use a two level naming scheme for zone file names.
For example, a slave server for the zone example.com might place
the zone contents into a file called ex/example.com
where ex/ is just the first two letters of the zone
name. (Most operating systems behave very slowly if you
put 100K files into a single directory.)
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