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source interfaces


Hierarchy Level


Configure the clock source that is used by the clock selection process on an interface.

  • (SCB only) Specify the primary clock source as the external-a interface and the secondary clock source as the external-b interface. The clock source is chosen using the clock selection process.

  • (SCBE only) Specify the external interface to select the external clock source.

  • (SCBE2 only) Specify the external-0/0 interface or the external-1/0 interface to select the external clock source.



Amount of time in milliseconds that a signal is held before being passed to the clock selection process.

Range: 300–1800 milliseconds

Default: 1000 milliseconds


Set the priority level of the clock source.

Range: 1 through 5

prc—Primary reference clock

prs —Primary reference source—Stratum 1

sec—SDH equipment clock

smc—SONET minimum clock

ssu-a—Synchronization supply unit A

ssu-b—Synchronization supply unit B

st2—Stratum 2

st3—Stratum 3

st3e—Stratum 3E

st4—Stratum 4


Force switching to a clock source, provided the clock source is enabled and not locked out. Only one configured source may be force-switched.


Clock source is not considered by the selection process. Lockout may be configured for any source.


Set the time for the port signal to be up before the port is opened to receive and transmit ESMC messages.

Range: 0 through 12 minutes

Default: 5 minutes


aggregated ethernet group name

Required Privilege Level

interface—To view this statement in the configuration.

interface-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 11.2R4.