[ntp:questions] NTP Limited Broadcast

Danny Mayer mayer at ntp.isc.org
Tue Mar 13 04:01:32 UTC 2007

Kevin D. Casey wrote:
> I am running NTP 4.2.2 on FreeBSD 6.2 broadcasting to clients on the
> broadcast address of an internal subnet which is
> The server is using on its network
> interface. The attached switch hardware on the subnet is able to
> receive the broadcasts and update its clock as an SNTP client. I have
> also verified the presence of UDP 123 broadcasts using Ethereal. I
> have a proprietary time recording device also attached to the same
> broadcast domain that appears to be unable to receive it's updates in
> this way. Although it is designed to listen for UDP 123 broadcast
> traffic, the manufacturer is claiming that it will only listen for
> broadcasts sent to However when I try to reconfigure
> NTPD to use instead of the broadcast
> stops working. Can anyone tell me how to configure NTPD to broadcast
> on -- Kevin D. Casey kevin at kdcasey.net 

See Bug #779 https://ntp.isc.org/bugs/show_bug.cgi?id=779

This has become a difficult issue to resolve. Although a socket gets set
up to accept broadcast packets packets sent to only get
delivered to the wildcard socket where all packets get dropped. I'm not
sure why this is but it looks like all O/S's seem to ignore the
configured socket for this case in favor of the wildcard socket. I'm
trying to research this issue.


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