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driskind 12-06-2018 11:34 AM
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.

dc.901 12-06-2018 12:09 PM
Do you know if the servers are listening?

Code:
nc -vu <server_IP> 123

driskind 12-06-2018 12:37 PM
Quote:
Originally Posted by dc.901 (Post 5934125)
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.

dc.901 12-06-2018 12:57 PM
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.

driskind 12-06-2018 01:10 PM
Quote:
Originally Posted by dc.901 (Post 5934145)
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.

driskind 12-06-2018 01:19 PM
Quote:
Originally Posted by driskind (Post 5934152)
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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