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Old 12-06-2018, 12:34 PM   #1
driskind
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ntp testing failure on 3 of 4 hosts in a cluster


Having trouble with ntp on 3 of 4 host servers in a cluster

When executing /usr/sbin/ntpq -p on on host, I get a delay in response (obviously it is trying) then:
localhost: timed out, nothing received

On two other hosts, when executing /usr/sbin/ntpq -p, it immediately returns
/usr/sbin/ntpq: read: Connection refused

the fourth host returns data from all registered time servers in /etc/ntp.conf

The servers are running OEL Linux.

Any guidance appreciated. I don't have elevated privileges on the host servers, so anything I get back will have to be passed onto the Linux administrator.
 
Old 12-06-2018, 01:09 PM   #2
dc.901
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Do you know if the servers are listening?

Code:
nc -vu <server_IP> 123
 
Old 12-06-2018, 01:37 PM   #3
driskind
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Quote:
Originally Posted by dc.901 View Post
Do you know if the servers are listening?

Code:
nc -vu <server_IP> 123
forgive my ignorance. Command nc is new to me; while I read up on it, when I executed it, I substituted both IP address and hostname for <server_IP>. Then it just stalled. apparently listening on port 123? Ctrl-C terminated the state of nc.

Long story short; I cannot tell if servers are listening on the 3 hosts where ntp apparently not working. The fourth host where ntp is working and ntpq returns results gives me the same result from the nc command.
 
Old 12-06-2018, 01:57 PM   #4
dc.901
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If remote host is listening, this is what you will see, in this example, I am using "0.centos.pool.ntp.org" as NTP server:


Code:
$ nc -vu 0.centos.pool.ntp.org 123
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.241.146.233:123.
nc (netcat) is what I use to determine if remote host is listening to a perticular UDP port. In this case of NTP, it should listen on port 123/UDP.
 
Old 12-06-2018, 02:10 PM   #5
driskind
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Quote:
Originally Posted by dc.901 View Post
If remote host is listening, this is what you will see, in this example, I am using "0.centos.pool.ntp.org" as NTP server:


Code:
$ nc -vu 0.centos.pool.ntp.org 123
Ncat: Version 7.50 ( https://nmap.org/ncat )
Ncat: Connected to 192.241.146.233:123.
nc (netcat) is what I use to determine if remote host is listening to a perticular UDP port. In this case of NTP, it should listen on port 123/UDP.
OK. Then apparently it is not listening as I am not getting anything back. At this point I have submitted a trouble ticket request to our linux administrators to review the problem and ( hopefully ) repair the issue.
 
Old 12-06-2018, 02:19 PM   #6
driskind
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Quote:
Originally Posted by driskind View Post
OK. Then apparently it is not listening as I am not getting anything back. At this point I have submitted a trouble ticket request to our linux administrators to review the problem and ( hopefully ) repair the issue.


dc.901 - problem was with /etc/ntp.conf, parameter "restrict default ignore" commented off, then service ntp restart cleared the problem. Thank you for your effort!
 
  


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