[ntp:questions] Packet loss on peer associations?

Dennis Hilberg Jr a.user at ntp.isc.org
Thu Feb 22 17:12:22 UTC 2007

> All,
> I have recently started peering two of my NTP servers. One is a primary 
> server, the other only has Internet-based sources of synchronisation. They 
> are attached to the same LAN, which is lightly loaded, as are the servers 
> themselves (CPU usage rarely exceeds 1% and there is little disk 
> activity).
> Quite often though, the association misses a beat (e.g. the reach number 
> reported by ntpq -p is 376 or another combination of mostly 1s and few 
> 0s). I would expect to see this in the presence of packet loss, but I 
> really don't think that that is the case here.
> Note that I have clamped both maxpoll and minpoll to 6 on both sides 
> (because otherwise the problem was even worse, whenever the two peers did 
> not agree on the poll interval).
> Is this a problem?
> (One server is running ntpq 4.2.3p41 at 1.1401-o under Linux 2.4.20 on a P4, 
> the other ntpq 4.2.2p4 at 1.1585-o under Linux 2.4.31 on a soekris Geode).
> Thanks, Jan

I have the same question with a similar setup.  I have two Stratum 2s peered 
with each other.  Both are Linux machines running on the same LAN with 
little traffic on the LAN itself, both have light system loads, both are 
running ntp 4.2.4, and each have their own sychronization sources.  One 
server is a pool server and the other server is not visible to the internet. 
Running 'ntpq -p' on each server routinely shows its peer with a reach of 
376, while the rest of the synchronization sources show 377.  I also don't 
believe packet loss is an issue here.  Is this typical behavior with peered 



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