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Ntp Synchronization Error

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5. How does it work?

This section

What Is Ntp Offset

will try to explain how NTP will construct and maintain a working ntp offset meaning time synchronization network.

5.1. Basic Concepts

To help understanding the details of planning,

Ntp Stratum 16

configuring, and maintaining NTP, some basic concepts are presented here. The focus in this section is on theory.

1. Time References5.1.1.1. What is a reference clock?5.1.1.2. How will NTP use a reference clock?5.1.1.3. How will NTP know about Time Sources?5.1.1.4. What happens if the Reference Time changes?5.1.1.5. What is a stratum 1 Server?2. Time Exchange5.1.2.1. How is Time synchronized?5.1.2.2. Which Network Protocols are used by NTP?5.1.2.3. How is Time encoded in NTP?5.1.2.4. When are the Servers polled?3. Performance5.1.3.1. How accurate will my Clock be?5.1.3.2. How frequently will the System Clock be updated?5.1.3.3. How frequently are Correction Values updated?5.1.3.4. How reliable are those Error-Estimates?5.1.3.5. What is the Limit for the Number of Clients?4. Robustness5.1.4.1. What is the stratum?5.1.4.2. How are Synchronization Loops avoided?5. Tuning5.1.5.1. What is the allowed range for minpoll and maxpoll?5.1.5.2. What is the best polling Interval?6. Operating System Clock Interface5.1.6.1. How will NTP discipline my Clock?1. Time References5.1.1.1. What is a reference clock?

A reference clock is some device or machinery that spits out the current time. The special thing about these things is accuracy: Reference clocks must be accurately following some time standard.

Typical candidates for reference clocks are (very expensive) cesium clocks.

Application ServicesTroubleshoot and AlertsConfiguration Example and TechNotes Network Time Protocol (NTP) Issues Troubleshooting and Debugging Guide Download Print Available Languages Download Options PDF (28.8 KB) View with Adobe Reader

Ntp Jitter

on a variety of devices Updated:Aug 17, 2013 Document ID:116161 Contents Introduction NTP ntp stratum levels show Commands show ntp association show ntp association detail show ntp status Troubleshooting NTP with Debugs NTP Packets Not

Ntp Time Sync Windows

Received NTP Packets Not Processed Loss of Synchronization debug ntp validity debug ntp packets debug ntp sync and debug ntp events NTP clock-period Manually Set Related Information Introduction This document describes the use http://www.ntp.org/ntpfaq/NTP-s-algo.htm of debugs in order to troubleshoot Network Time Protocol (NTP) issues, as well as the output from key show ntp commands. NTP show Commands Before you look at the cause of NTP problems, you should understand the use of and output from these commands: show ntp association show ntp association detail show ntp status Note: Use the Command Lookup Tool (registered customers only) in order to http://www.cisco.com/c/en/us/support/docs/ip/network-time-protocol-ntp/116161-trouble-ntp-00.html obtain more information on the commands used in this section. Note: The Output Interpreter Tool (registered customers only) supports certainshow commands. Use the Output Interpreter Tool in order to view an analysis of show command output. show ntp association An NTP association can be a peer association (one system is willing to synchronize to the other system or to allow the other system to synchronize to it) or a server association (only one system synchronizes to the other system and not the other way around). This is an example of output from the show ntp association command: CLA_PASA#sh ntp association address ref clock st when poll reach delay offset disp~127.127.7.1 127.127.7.1 9 50 64 377 0.0 0.00 0.0~10.50.44.69 10.50.36.106 5 21231 1024 0 3.8 -4.26 16000.+~10.50.44.101 10.50.38.114 5 57 64 1 3.6 -4.30 15875.+~10.50.44.37 10.50.36.50 5 1 256 377 0.8 1.24 0.2~10.50.44.133 10.50.38.170 5 12142 1024 0 3.2 1.24 16000.+~10.50.44.165 10.50.38.178 5 35 256 357 2.5 -4.09 0.2+~10.50.38.42 86.79.127.250 4 7 256 377 0.8 -0.29 0.2*~10.50.36.42 86.79.127.250 4 188 256 377 0.7 -0.17 0.3+~10.50.38.50 86.79.127.250 4 42 256 377 0.9 1.02 0.4+~10.50.36.50 86.79.127.250 4 20 256 377 0.7 0.87 0.5* master (synced), # master (u

Start here for a quick overview of the site Help Center Detailed answers to any questions you might have Meta Discuss the workings and policies of this site http://serverfault.com/questions/461752/ntpdate-and-ntpd-failing-to-sync-clock-on-linux About Us Learn more about Stack Overflow the company Business Learn more about hiring developers or posting ads with us Server Fault Questions Tags Users Badges Unanswered Ask Question _ Server Fault is https://support.microsoft.com/en-us/kb/875424 a question and answer site for system and network administrators. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The ntp offset best answers are voted up and rise to the top ntpdate and ntpd failing to sync clock on Linux up vote 10 down vote favorite 2 I have a strange problem with one of my servers. ntpd and ntpdate fail to work, but debugging shows no errors at all. At first I thought maybe a local or network firewall was blocking UDP port 123, but that ntp synchronization error is not the case- this server can talk UDP port 123 (the ntp protocol) to the Internet and get answers. Let me demonstrate the issue. date -s "30 DEC 2012 02:30:00" - works, so I can successfully set the clock without error. ntpq -pn pool.ntp.org - works, I do get detailed time data from the timeserver, and proves UDP packets are functioning. ntpdate -d pool.ntp.org - debug mode works, shows a ton of debug data and shows the current time offset: 30 Dec 02:38:56 ntpdate[19267]: step time server 208.97.140.69 offset 228.234554 sec All looks normal, until: ntpdate pool.ntp.org - after a 4.7 second pause, it returns: 30 Dec 02:41:29 ntpdate[19274]: no server suitable for synchronization found Similar problem running ntpd, it does not update the clock. After ntpd is started, ntpq -pn results in all refid's forever stuck on .INIT. which means they cannot sync. /var/lib/ntp/drift is the driftfile setting in ntp.conf, which is chmod 644 and owned by ntp:ntp, same as all my other systems. I tried a dozen other ntp time servers, disabled iptables firewall, and confirmed the datacenter is not filtering udp traffic. Any ideas what is stopping ntpd and ntpdate from sync

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