Installing and Administering Internet Services

Chapter 7 311

Conﬁguring the Network Time Protocol (NTP)

Advanced NTP Topics

appears:

• The remote (server name) column shows hosts speciﬁed in the local

host’s conﬁguration ﬁle plus other hosts that are conﬁgured to be

peers with the local host. The host address can be preceded by a

special character. These characters indicate the fateof the peer server

in the clock selection process. The characters and their meanings are

as follows: preceded with a ‘*’ indicates the current synchronization

source. A ‘-’ indicates a host that was not considered for

synchronization, while a ‘+’ indicates a host that was considered for

synchronization.

— ‘*’ is selected for synchronization.

— ‘#’ is selected for synchronization, but distance exceeds maximum.

— ‘o’ selected for synchronization, PPS signal in use.

— ‘+’ included in the ﬁnal synchronization selection set.

— ‘x’ designated false ticker by the intersection algorithm.

— ‘.’ picked out from the end of the candidate list.

— ‘-’ discarded by the clustering algorithm.

— ‘blank’ discarded due to high stratum and/or failed sanity checks.

• The refid (reference identiﬁcation) column shows the current source

of synchronization for the remote host. ‘.WWVB.’ indicates that the

host uses a radio clock that receives time signals from the U.S.

government radio station WWVB.

• The st (stratum) column shows the stratum level of the remote host.

• The t (types) columns shows the available types, which include

l=local (such as a GPS clock), u=unicast (this is the most common

Table 7-7 ntpq Output Showing Known NTP Hosts

remote refid st t when poll reach delay offset disp

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

*GPS_HP(1) GPS 0 l 48 64 377 0.00 0.516 4.19

hpps.cup.hp cupertino 3 u 467 1024 377 7.20 -12.430 15.67

+server2 WWVB 1 u 173 256 377 279.95 20.56 16.40

+node1 node3 2 u 131 256 373 9.89 16.28 23.25