There are several different modes that hosts can be directly configured to operate in with respect to synchronization with other hosts: client mode, broadcastclient mode, and symmetric active mode.
In client mode, a host polls other hosts to get the current time. From among all of the hosts polled, the local host selects one with which to synchronize. To configure your host this way, include a server statement in your host's configuration file. The name or IP address of each time server to be polled must be specified in the server statement.
In broadcastclient mode, a host does no polling at all. Rather, it listens for NTP packets broadcast over the network. From among all of the broadcasting hosts, the local host selects one with which to synchronize. To configure your host this way, include a broadcastclient yes statement in your host's configuration file. For this mode to function, the local time servers must be configured in broadcast mode with the broadcast configuration statement.
Finally, in symmetric active mode, a host polls other hosts and responds to polls from those hosts. In addition, hosts retain time-related information about the hosts with which they are communicating. To configure your host this way, include a peer statement in your host's configuration file. The name or IP address of each time server must be specified in the peer statement.
A general guideline is to configure all hosts, except those at the highest strata of the synchronization subnet (those furthest away from stratum 1 servers), to operate in symmetric active mode. For those hosts that are at the highest strata, you have a choice: configure them to operate either in client mode or in broadcastclient mode. You should consider opting for broadcastclient mode if your hosts are on a high-speed LAN that supports broadcasts efficiently, especially if the hosts number more than twenty or so.
If you do opt for broadcastclient mode on those hosts, you must
configure the time servers on the local network to be both in
broadcast mode (to send broadcast NTP packets on the
local network) and in symmetric active mode (to poll hosts at