6.2. Orphan mode

Orphan Mode is the stated replacement for the UndisciplinedLocalClock. It was added to ntp-4.2.2.

Orphan Mode allows a group of ntpds to automonously select a leader in the event that all real time sources become unreachable (i.e. are inaccessible).

Orphan Mode is enabled by adding the line tos orphan N anywhere in ntp.conf. The N specifies the stratum at which this ntpd will switch to Orphan Mode. For example, an ntpd using tos orphan 6 will not switch to Orphan Mode as long as a time source of strata 1 through 5 is reachable.

In addition to the tos orphan line all members of the Orphan Mode group must be configured in a mesh (i.e. they must all be clients / peers of each other). Any NTP association mode may be used to set up this mesh.

NTP versions prior to 4.2.4p5 and 4.2.5p101 will not start up properly in Orphan Mode unless at least one time source is configured in ntp.conf. If no time sources are specified the refid stays at .INIT. and the rootdispersion continually increases. This makes these versions unsuitable for use as stand alone Orphan Mode servers in a time island.

NTP versions after, and including, 4.2.5p101 will start up correctly in pure Orphan Mode.