Symmetricom Time Server Manual Do Utilizador

Appendix B: MD5 Authentication and NTP Broadcast Mode

Authentication was configured off by default for NTP version 3, but is configured on by 
default for version 4.  This means that NTP version 4 must use authentication, like MD5, 
for broadcast time to work.  To have it otherwise, you must specifically turn 
authentication off in the “ntp.conf” file of the NTP time client.  

For the NTP timeserver, authentication may be on or off - it does not matter.  As an 
example, here is a sample “ntp.conf” file. 

server

192.168.1.49

server 206.54.0.20

server

206.54.0.21

broadcast

192.168.1.255

This file is stored on the Symmetricom timeserver in its Flash disk drive in the “/etc” 
directory.   

The critical line is: 

broadcast 192.168.1.255.

  

• This line turns on the periodic broadcast of NTP time packets to the local LAN.  

This IP address (the first three octets: 192.168.1) is a network address.  

The LAN portion of the address, the last octet in this case, is set to all ones.  You 
may use all zeros for most LANs as the LAN address, instead of all ones.  This 
address allows NTP time packets to be received by all hosts on the local LAN 
including the NTP time client.  Ask your system administrator what your LAN 
broadcast address is for your particular network and substitute it for the address in 
this example.