Linux – NTP local query always times out

centoslinuxntpredhat

I have a CentOS 6.4 server, it does not have any iptable rules, it runs NTP daemon as service using the following configuration:

  driftfile /var/lib/ntp/drift

  server 0.pool.ntp.org
  server 1.pool.ntp.org
  server 2.pool.ntp.org
  server 3.pool.ntp.org

  restrict default ignore
  restrict 127.0.0.1

When I run ntpq to query peers, the following response is received:

ntpq> peers
localhost.localdomain: timed out, nothing received

dig shows that:

localhost.localdomain.  86400   IN  A   127.0.0.1

Why doesn't ntp query work?

Best Answer

On RHEL / CentOS 6 and 7, for whatever reason ntpq tries to query the IPv6 loopback at ::1 instead of the IPv4 loopback at 127.0.0.1. With this in mind, I added this line to my /etc/ntp.conf file:

restrict ::1

Saved the file then restarted ntpd 

service ntpd restart

now the command:

ntpq -p

works as expected. (This is the same as running ntpq in command-line mode and then issuing the peers command.)

I prefer this solution since you do not have to enable communications with ntpd via a potentially public Ethernet interface, which may be a security concern.

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