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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide
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Chapter4 Troubleshooting the System Managing the Cisco uBR7246 VXR Clock Card
Force Alternate Clock
Toselect the external timing source when the clock card is in holdover mode, use the cable clock force
globalconfiguration command. To disable the selection and return to the default, use the no form of this
command.
cable clock force {primary |secondary}
nocable clock force
Setting the cable clock to primary forces the primary source to act as the clock reference. Setting the
cable clock to secondary forces the secondary source to act as the clock reference.
Theclock card automatically uses the primary external source, if available. If the primary source fails,
theclock card enters holdover mode and after a few seconds, switches to the secondary external source.
The clock card switches back to the primary source when it becomes available.
Note This command overridesthe default behavior of the clock card, when the clock card is in
holdover mode. If the clock card is not in holdover mode, this command is ignored. You
cannot force the reference to a port if the clock card is in free-running mode. The clock
card enters holdover mode if the forced reference is lost, even if the other external
reference is available.
Set Midplane TDM Clock as Primary Reference
Tomake the midplane TDM clock the primary timing reference for the clock card, use the cable clock
source-midplaneglobal configuration command. To disable the selection and return to the default, use
the no form of this command.
cable clock source-midplane
Note Becausethe clock card automatically provides the timing reference to the midplane TDM
clock,the midplane cannot in turn act as the reference for the clock card. This means that
the cable clock source-midplane command does not take effect unless a port adapter is
configured as the primary clock reference source for the midplane.
Caution Although the cable clock source-midplanecommand is configurable, it is ignored, until
a port adapter that can serve as the midplane clock reference source is supported in the
Cisco uBR7246 VXR. Currently, there are no port adapters on the Cisco uBR7246 VXR
that support this.
Display Clock Values
To display clock reference status information for the clock card, use theshow cable clock privileged
EXEC command:
show cable clock