Installing and Administering Internet Services

302 Chapter7
Configuring the Network Time Protocol (NTP)
Advanced NTP Topics
provide time to which the named host may be synchronized. (The local
host is a client of the named host.) In addition, server statements are
used to configure external clocks (radio clocks or local system clocks) for
stratum-1 servers. Refer to “Configuring External Clocks” on page 303
for more information.
broadcast host | broadcast_address specifies that the xntpd daemon
in the local host transmits broadcast NTP messages to a named address,
usually the broadcast address on your local network. (The local host is a
broadcaster.)
With the peer, server,orbroadcast statement, you can also specify one
or more of the following options:
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 305.
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
XXX”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.