[ntp:questions] NTP makes a time jump

karpekin at gmail.com karpekin at gmail.com
Thu Jul 4 11:42:32 UTC 2013


Hello,
I have a problem with NTP configuration when the client loses uplink connection for some time and then re-establishes it. 
ntp.conf:

tos maxdist 4
server 10.9.2.80 iburst
server  10.10.2.101 iburst
server  10.10.52.111 iburst
server 127.127.1.0
fudge 127.127.1.0 stratum 12 

I do the following:
1. kill the NTPD process, 
2. disconnect the uplink to real servers, 
3. change the local clock time to +3 sec 
4. reboot the system.
System comes up and after a while syncs to itself. After it starts to provide my "fake" time reference (+3sec) to clients downstream, I plug in the uplink, so my client is able to see the 3 servers defined in the config above. And as soon as it established the connection and peered to one of them, I see the -3 sec time jump. I was expecting that NTPD will slowly start to correct the time, but it jumps. 
Can you please explain if that behavior is by NTP design? Maybe I have something misconfigured, and if so, how to force NTPD not to make jumps? 
Thank you,
Igor.



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