Configuring Network Time Protocol (NTP) service

A complex NTP configuration scenario

In this example, the hosts acapulco, seattle, and moscow are stratum 2 time servers in the mynet.com network. ``An example synchronization subnet'' shows the relationships between these time servers, their clients, and Internet time servers in stratum 1 which are external to the mynet.com network. The arrows show the direction in which information about the time flows.

An example synchronization subnet

NOTE: The stratum 1 servers shown are used as examples only. In practice, these servers may no longer exist or be publicly accessible.

The servers are associated as follows:

acapulco polls two stratum 1 servers, clock.llnl.gov and clepsydra.dec.com, in client mode.
seattle polls two stratum 1 servers, ntp.olivetti.com and ntp1.ossi.com, in client mode.
moscow polls two stratum 1 servers, apple.com and norad.arc.nasa.gov, in client mode.
acapulco polls seattle and moscow as a peer.
seattle polls acapulco and moscow as a peer.
moscow polls acapulco and seattle as a peer.
chicago and the rest of the machines at mynet.com are clients at stratum 3 and listen for broadcast NTP packets from the three stratum 2 hosts, acapulco, seattle, and moscow.

The following configuration files configure mynet.com to match the topology discussed in ``Guidelines for implementing NTP''. All hosts can be configured dynamically with xntpd. There are no restrictions on which hosts can be designated as time servers in a given host's configuration file.

Configuration of the stratum 2 server acapulco

This is the ntp.conf file for acapulco:

# NTP configuration file for 172.16.246.16 (acapulco.mynet.com) # server 128.115.14.97 # clock.llnl.gov server 16.1.0.22 # clepsydra.dec.com peer seattle.mynet.com peer moscow.mynet.com

broadcast 172.16.246.255

driftfile /etc/inet/ntp.drift keys /etc/inet/ntp.keys requestkey 65534 controlkey 65535

This is the ntp.keys file for acapulco:

   2313      M    APassword
   65534     M    NoSecret
   65535     M    BadKey

Configuration of the stratum 2 server seattle

This is the ntp.conf file for seattle:

# NTP configuration for seattle (172.16.246.11) # server 129.189.134.6 # ntp.olivetti.com server 192.240.4.1 # ntp1.ossi.com peer acapulco peer moscow

broadcast 172.16.246.255

driftfile /etc/inet/ntp.drift keys /etc/inet/ntp.keys requestkey 65534 controlkey 65535

This is the ntp.keys file for seattle:

   2313      M    APassword
   65534     M    NoSecret
   65535     M    BadKey

Configuration of the stratum 2 server moscow

This is the ntp.conf file for moscow:

# NTP configuration file for 172.16.246.7 (moscow.mynet.com) # server 130.43.2.2 # apple.com server 192.52.195.10 # norad.arc.nasa.gov peer seattle.mynet.com peer acapulco.mynet.com

broadcast 172.16.246.255

driftfile /etc/inet/ntp.drift keys /etc/inet/ntp.keys requestkey 65534 controlkey 65535

This is the ntp.keys file for moscow:

   2313      M    APassword
   65534     M    NoSecret
   65535     M    BadKey

Configuration of the broadcast clients

This is the generic ntp.conf file for broadcast clients such as chicago:

   # Peer configuration used by all broadcast clients at mynet.com
   #
   broadcastclient  yes
   broadcastdelay   0.0500
   driftfile        /etc/inet/ntp.drift
   keys             /etc/inet/ntp.keys
   requestkey  65534
   controlkey  65535

This is the ntp.keys file:

   2313      M    APassword
   65534     M    NoSecret
   65535     M    BadKey