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Configuring the Clock Source on SONET/SDH Interfaces

 

For interfaces such as SONET/SDH that can use different clock sources, you can configure the source of the transmit clock on each interface. The source can be internal or external. The default source is internal, which means that each interface uses the router’s internal Stratum 3 clock.

For DS3 channels on a channelized OC12 interface, the clocking statement is supported only for channel 0; it is ignored if included in the configuration of channels 1 through 11. The clock source configured for channel 0 applies to all channels on the channelized OC12 interface. The individual DS3 channels use a gapped 45-MHz clock as the transmit clock.

To configure the loop timing:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the clocking external statement.

To explicitly configure line timing on an interface:

  1. In configuration mode, go to the [edit interfaces interface-name] hierarchy level.
  2. Include the clocking internal statement.
Note

On Channelized SONET/SDH PICs, if you set the parent (or the master) controller clock to external, then you must set the child controller clocks to the default value—that is, internal.

For example, on the Channelized STM1 PIC, if the clock on the Channelized STM1 interface (which is the master controller) is set to external, then you must not configure the CE1 interface (which is the child controller) clock to external. Instead you must configure the CE1 interface clock to internal.