[ntp:questions] NTP request retry?

Rob nomail at example.com
Tue Jan 28 09:00:48 UTC 2014


Brian Inglis <Brian.Inglis at SystematicSw.ab.ca> wrote:
> On 2014-01-27 14:45, Rob wrote:
>> Rick Jones <rick.jones2 at hp.com> wrote:
>>> Brian Inglis <Brian.Inglis at systematicsw.ab.ca> wrote:
>>>
>>>> You don't specify which system and devices you are using,
>>>> so here are a couple of articles about changing ARP timeouts:
>>>> http://www.embeddedsystemtesting.com/2013/01/arp-timeout-value-for-linux-windows.html
>>>> http://support.microsoft.com/kb/949589
>>>
>>> And if indeed these are all the OP's own systems, he can add
>>> hardwired, "permanent" ARP cache entries via the arp command (under
>>> most *nixes at least).
>>
>> I'm still not sure if ARP is really the problem, but fixing the
>> clients to maxpoll 6 seems to cure it.
>> (at least the reach now sticks at 377)
>>
>>> If a mix of wired and wireless is involved, if there is some way to get
>>> traces at the point where the two join that would be goodness.
>>
>> If both would be WiFi, I would point at the WiFi.  However, one is
>> connected to the wired network (a switch where the server is connected
>> as well).
>>
>> I can ping it as much as I like, no loss:
>> 1571 packets transmitted, 1571 received, 0% packet loss, time 20468ms
>> rtt min/avg/max/mdev = 0.702/0.845/1.168/0.090 ms
>>
>> But when ntpd is allowed to climb to 1024-second polls, it gets almost
>> no replies.
>
> Check the server wrappers/firewall/switch allowing incoming unsolicited
> packets on port 123. If you "enable stats"+"statistics rawstats" or watch
> packets on the server, you should see whether requests are making it into
> the server and replies out. As other posters have suggested, it could be
> a port blocking timeout anywhere along either path between the two ntpds.

The path is only a gbit switch and for the Wifi a Wifi access point
in bridge mode.
There is no firewall on the server and on one of the clients.
The other client has a static firewall rule that accepts traffic from
the lan range, including the server.
The behaviour of the two clients is the same.



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