[ntp:questions] How to specify interface for multicastclient

Charles Elliott elliott.ch at comcast.net
Fri Jan 15 11:11:21 UTC 2016

How to configure broadcast mode is in confopt.html in the NTP documentation
that comes with the Meinberg distribution for Windows.  It is easy to set up
too.  For the broadcast delay option, I averaged the delay between computers
from loopstats and divided by 2.  For me, back in the day when I was running
several computers for processing SETI at Home work units, it was a huge
success.  Jitter went down to almost nothing, and the computers were in
lockstep with each other timewise, but a LAN in a home environment is VERY
lightly loaded.  The results could be different on a LAN with a lot of

BTW, the way I found the documentation again for broadcast mode was by
pointing AstroGrep at C:\Program Files (x86)\NTP\doc\HTML, searching for
"broadcast," and then reading the files located until I recognized the
correct page.  Since the letter 'C' comes near the head of the alphabet, it
did not take long.

Charles Elliott

-----Original Message-----
From: questions
[mailto:questions-bounces+elliott.ch=comcast.net at lists.ntp.org] On Behalf Of
Brian Inglis
Sent: Thursday, January 14, 2016 3:16 AM
To: questions at lists.ntp.org
Subject: Re: [ntp:questions] How to specify interface for multicastclient

On 2016-01-13 20:10, Brian Inglis wrote:
> On 2016-01-13 14:30, brian utterback wrote:
>> I am sure this has been asked before but I can't find the answer. On 
>> a multihomed system, is there anyway to specify which interfaces you 
>> want multicastclient to listen on? If so, how. If not, why not? I 
>> would have expected it to listen on all interfaces, but it doesn't do
> Relevant links:
> https://www.eecis.udel.edu/~mills/ntp/html/miscopt.html#interface
> https://www.eecis.udel.edu/~mills/ntp/html/discover.html#bcst
> https://www.eecis.udel.edu/~mills/ntp/html/confopt.html#broadcast
> https://www.eecis.udel.edu/~mills/ntp/html/confopt.html#multicastclien
> t
> Address options:
> https://en.wikipedia.org/wiki/Multicast_address
> https://tools.ietf.org/html/rfc2365
> http://tools.ietf.org/html/rfc5771
> http://www.iana.org/assignments/multicast-addresses/multicast-addresse
> s.xhtml

e.g. you should be able to set multicast address as the broadcast
address on one interface and on the other, specify two lines with
the broadcast addresses in ntp.conf, and have all clients specify both as
the multicastclient addresses in their ntp.conf.
If the servers are used for anything but NTP, YMMV: see last 4 links.

Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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