[ntp:questions] why does asterisk still show after the ntp server is shutdown?

Rob nomail at example.com
Fri Nov 16 20:40:44 UTC 2012


unruh <unruh at invalid.ca> wrote:
> On 2012-11-16, Rob <nomail at example.com> wrote:
>> unruh <unruh at invalid.ca> wrote:
>>> AFter a while it will. Right now it has only missed three pollings of
>>> the server ( and since ntpd throws away 7 out of 8 polls anyway that is
>>> too little) so wait another 10 hours and see if the * remains. Your
>>> machine has no way of knowing if the other machine is only temporarily
>>> disconnected due to some network problem, of has beenswitched off. There
>>> is not return ntp signal saying "computer turned off". You know it is,
>>> but your compter does not. 
>>
>> There is, but ntpd does not listen to it.
>
> ?? there is what? A return signal saying "the computer is turned off"?
> exactly what would it be that is sending that return signal, since the
> computer cannot. 

The next router upstream will send an ICMP "destination unreachable"
when it cannot resolve the IP address into a hardware address, which
normally happens when it gets no reply to its ARP requests.

However, those ICMP "destination unreachable" are often ignored by
applications, including ntpd.  Some people even block them at their
firewalls.



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