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When using ntpdate-d to query, we will find that there are two error messages that lead to noserver suitable for synchronization found. Error 1 is serv erdropped:Stratatoohigh , error 2 is serv erdropped:nodata We will analyze them one by one

1Serverdropped

Error 1: serv erdropped:Stratatoohigh

When running ntpdateserver IP on NTP client, the error of no server suitable for synchronization found appears

In the NTP client, use ntpdate – dserver IP to check and find “serv” erdropped:stratatoohigh ”And “stratum16” is displayed. Under normal circumstances, the value range of stratum is “0 ~ 15”

This is because ntpserver is not synchronized with itself or its server

The following definition is to keep NTP server and itself synchronized. If the servers defined in/ntp.conf are not available, local time will be used as NTP service to provide NTP clients

server127.127.1.0

fudge127.127.1.0stratum8

After restarting NTP service on NTP server, it takes a period of time for NTP server itself or its server to synchronize. This process may take 5 minutes. During this period, when the client runs ntpdate command, there will be an error of no server suitable for synchronization found

So how do you know when NTP server completes the synchronization process with itself

Use the command on ntpserver:

#watchntpq-p

The screen appears:

Every2.0s:ntpq-pThuJul1002:28:322008

remoterefidsttwhenpollreachdelayoffsetjitter

======================================================

192.168.30.22LOCAL(0)8u226412.113179133.0.001

LOCAL(0)LOCAL(0)10l216410.0000.0000.001

Note that this local is the NTP server synchronized with itself

Note the value of reach. After the NTP server service is started, the value increases continuously from 0. When it increases to 17, there are five changes from 0 to 17. Each time is the number of seconds of the value of poll, which is 64 seconds * 5 = 320 seconds

If it fails to synchronize NTP server from NTP client, use ntpdate – d to query the detailed error information, and then make a judgment

2nodata

Error 2. Serv erdropped:nodata

When executing netdate – d from the client, the error message is as follows:

transmit(192.168.30.22)

transmit(192.168.30.22)

transmit(192.168.30.22)

transmit(192.168.30.22)

transmit(192.168.30.22)

192.168.30.22:Serv erdropped:nodata

server192.168.30.22,port123

…..

28Jul17:42:24ntpdate[14148]:noserversuitableforsynchronizationfound

There are two possible reasons for this problem

1. Check the version of NTP. If you use the version after ntp4.2 (including 4.2) and use notrust in the definition of restrict, the above error will be caused

Use the following command to check the version of NTP:

#ntpq-cversion

Here’s a description from NTP’s official website:

Thebehaviorofnotrustchangedbetweenversions4.1and4.2.

In4.1(andearlier)notrustmeant”Don’ttrustthishost/subnetfortime”.

In4.2(andlater)notrustmeans”IgnoreallNTPpacketsthatarenotcryptographicallyauthenticated.”Thisforcesremotetimeserverstoauthenticatethemselvestoyour(client)ntpd

Solution:

Get rid of notrust

2. Check the firewall of ntpserver. It may be that the firewall of the server has blocked the upd123 port

You can use the command

#serviceiptablesstop

To turn off the iptables service, and then try to synchronize from the NTP client. If it is successful, it proves that it is a firewall problem, and you need to change the iptables settings