Installing and Administering Internet Services

218 Chapter 7
Configuring NTP
Configuration
key number specifies that the NTP packets sent to the named host are
encrypted using the key that is associated with number. The
authentication feature of xntpd must be enabled. See “Configuring
Authentication” on page 221.
version 1 must be specified if xntpd will be requesting time from a
host that is running ntpd, a daemon that is based on version 1 of the
NTP protocol. version 2 must be specified if xntpd will be requesting
time from a host that is running an xntpd implementation that is based
on version 2 of the NTP protocol. If either of these options is not
specified, xntpd sends out version 3 NTP packets when polling the host;
if the host is a version 1 or 2 implementation, the packets will be
discarded.
prefer specifies that the named host should be the primary source for
synchronization when it is one of several valid sources. This option is
most useful for a time server on a high-speed LAN that is equipped with
an external time source, such as a radio clock. As mentioned in
“Guidelines for Configuration” on page 215, synchronization may be
provided by outside sources. However, the local time server should be the
preferred synchronization source.
The other role that you can define in the configuration file is that of a
broadcast client. The statement broadcastclient yes indicates that
the local host should listen for and attempt to synchronize to broadcast
NTP packets. The optional statement broadcastdelay seconds
specifies the default round trip delay to the broadcaster.
NOTE Every node in an NTP hierarchy must have either a server statement
or a broadcastclient yes statement in its configuration file. Every
node must have an upper-level server. A stratum-1 server must also have
a server statement in its configuration file, which specifies a radio clock
or internal system clock as a time source.
Note that if the local host is to assume the role of a server in providing
time to clients, there is no configuration of this role on the local system.
Instead, the configuration file on the client system would contain a
server statement with the name or IP address of the host.
Also note that if authentication is enabled on the local host, the roles you
configure are subject to the authentication process. For example, the
local host can be configured as a peer or a client of a stratum-1 server,