[ntp:questions] Troubleshooting who's at fault

David Mills mills at udel.edu
Fri Jun 26 20:41:09 UTC 2009


Dave,

The reported configuration is as bad as it gets and is exactly what 
orphan mode was designed to avoid.

For record ans as described on the Mitigation Algorithms and the Prefer 
Peer page, a loop is detected if he is synchronized to me or if he and I 
are syncronized to the same IP address. There is no distinction based on 
stratum. Yes, two hombres happen to use the same refclock address and 
configuring each other will see a loop.

Dave

Dave Hart wrote:

>On Fri, Jun 26, 2009 at 7:04 AM, David Woolley wrote:
>  
>
>>Harlan Stenn wrote:
>>
>>    
>>
>>>If you are using LOCAL as a fallback on your client, and your upstream
>>>server is using LOCAL ias the name for its PTS-sync'd refid, then the client
>>>just sees that the 2 sources it knows about are using the same refid and
>>>will flag that as a loop.
>>>
>>>      
>>>
>>That doesn't sound sensible. Â It implies you cannot peer two machines
>>that have the same reference clock technology. Â Is the problem that
>>reference clocks, as a special case, use the same reference ID as the
>>stratum 1 server that uses them, and, by the time the check is done, the
>>distinction between a reference clock and a server has been lost?
>>    
>>
>
>I think another part of the equation that causes the loop detection to
>fire here is the reference clock has been fudged to a numerically
>higher stratum.  With the refclock left at the default stratum 0 (and
>so the ntpd attached at stratum 1) the loop detection will not fire
>for two peered ntpds using the same driver and unit number.  In other
>words, I believe the loop detection treats stratum 1 refid's
>specially.
>
>Cheers,
>Dave Hart
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