Configuring the Clock Source

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 (also called line timing or normal) or external (also called loop timing). The default source is internal, which means that each interface uses the routing platform'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. For more information, see Clock Sources on Channelized Interfaces.

NOTE: On channelized STM1 interfaces, you should configure the clock source at one side of the connection to be internal (the default JUNOS configuration) and configure the other side of the connection to be external.

To configure loop timing on an interface, include the clocking external statement at the [edit interfaces interface-name] hierarchy level:

[edit interfaces interface-name]

clocking external; 

To explicitly configure line timing on an interface, include the clocking internal statement at the [edit interfaces interface-name] hierarchy level:

[edit interfaces interface-name]

clocking internal;