This is a discussion on Re: NTP Limited Broadcast - NTP ; Kevin Casey wrote: > I must say I am humbled by the response to my question. My knowledge of > IP networking is rudimentary by comparison. I would like to clarify that > I did not expect to be crossing ...
Kevin Casey wrote:
> I must say I am humbled by the response to my question. My knowledge of
> IP networking is rudimentary by comparison. I would like to clarify that
> I did not expect to be crossing a gateway boundary using the limited
> broadcast. According to the vendor, because all communication with the
> device is achieved via the broadcast address, its IP address is
> irrelevant and therefore not documented. I only know that the device is
> designed to listen for UDP 123 broadcasts on 255.255.255.255. Nor does
> the vendor require that I use 192.168.144.0/24 or any particular subnet
> or host address. I just need to make my NTP server broadcast UDP 123 to
> 255.255.255.255 on a connected interface where that interface shares a
> broadcast domain with his device. I suppose this would be similar to the
> behavior of a DHCP client broadcasting DHCPDISCOVER messages on its
> local physical network. However the ntp.conf(5) man page states "Note
> that local broadcast messages go only to the interface associated with
> the subnet specified, but multicast messages go to all interfaces."
> Evidently 192.168.144.120/24 is not associated with a "broadcast
> 255.255.255.255" command in ntp.conf. So I am wondering if there is any
> network interface configuration possible in FreeBSD 6.2 that will permit
> NTPD to broadcast UDP 123 to 255.255.255.255 on that interface.
There's no problem broadcasting *TO* that address. The problem lies in
*RECEIVING* packets sent to that address. I'm researching ways to
resolve this issue but it may take some time. You could change the code
(specifically ntpd/ntp_io.c) to accept packets on the wildcard sockets.
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