Why is an interface in Down state on a CE series switch

If the indicator of a connected interface on a CE series switch is off, the interface does not go Up. You can run the display interface command on the switch to view the interface status.

Common causes:
1. The interface is manually shut down.
2.The cable or optical fiber is faulty.
3. The optical module is faulty.
4. The local and remote interfaces fail to negotiate parameters including the duplex mode and rate.

Recommended solutions:
1. Check whether the interface has been manually shut down using the shutdown command. If so, run the undo shutdown command in the interface view to enable the interface.
2. Connect the interface to another interface, and replace the optical module, optical fiber, or cable on the interface to check whether the interface, optical module, or optical fiber/cable is faulty.

If the fault persists, see section "Interface Troubleshooting" in the Troubleshooting - Hardware.

Other related questions:
How to restore an interface in ERROR DOWN(link-flap) state to Up state on a CE series switch
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