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

David Woolley david at ex.djwhome.demon.invalid
Fri Nov 16 22:14:56 UTC 2012


Rob wrote:

> 
> 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.

Only once the ARP cache times out, and only if the link level protocol 
uses ARP.
> 
> However, those ICMP "destination unreachable" are often ignored by
> applications, including ntpd.  Some people even block them at their
> firewalls.

They are difficult to handle for UDP based protocols, as the application 
has to specifically receive them and to correlate them with the specific 
request.



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