[ntp:questions] Broadcast mode

Martin Townsend mtownsend1973 at gmail.com
Mon Sep 12 09:02:33 UTC 2016


Hi,

We have a closed network of embedded devices that we want to keep in
sync, the actual time is not important but the fact that they are all
on the same time is.  One device is always the master so this is the
device that we want the others to synchronise to.

Reading the documentation broadcast mode looks perfect.  I'm currently
trying it out with the following configuration:

# Broadcast Server
broadcast 192.168.2.255
ttl 1

server 127.127.1.0
fudge 127.127.1.0 stratum 14

...

# Broadcast Client
broadcastclient

server 127.127.1.0
fudge 127.127.1.0 stratum 14

...


I've seen what look like valid messages being exchanged using tcpdump
but haven't seen any evidence that the times are converging but I
haven't really left it long enough. In the meantime I have read this
link
http://www.ntp.org/ntpfaq/NTP-s-config-adv.htm#AEN3658
which seems to indicate that this setup is not possible.  So my question is
Is broadcast mode with LCL a non started and if so what is the best
method for a private network that you need to keep in sync?

I'm using the latest version 4.2.8p8, built using Yocto for an ARM cortex A8.

Best Regards,
Martin.


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