An interface on a WLAN device fails to go Up

The possible causes are as follows:
- The interface is manually shut down.
- The power cable is faulty or the optical fiber does not meet requirements.
- If the interface is a combo interface, the working mode may be incorrectly configured.
- The duplex modes, rates, and negotiation modes are different on the connected interfaces.
- The device hardware is faulty.

Perform the following operations to rectify the fault:
1. If the interface is manually shut down, run the undo shutdown command in the interface view to enable it.
2. If the interface is an electrical interface or a combo interface working in electrical mode, check whether the power cable is faulty and securely connected on the local and remote devices.
If the interface is an optical interface or a combo interface working in optical mode, check whether the type and length of the optical fiber, and the transmission distance supported by the optical module meet requirements.

3. If the interface is a combo interface, run the display this command to check whether the interface mode is correctly configured.
- Run the combo-port auto or combo-port fiber command to set a combo interface to the auto or optical mode.
- Run the combo-port auto or combo-port copper command to set a combo interface to the auto or electrical mode.

4. Run the display interface [ interface-type [ interface-number ] ] command to check the rate, duplex mode, and negotiation mode of the interface. In the command, interface-type and interface-number specify the interface type and number, respectively.

- Check the Negotiation field.
If ENABLE is displayed, the interface works in auto-negotiation mode.
If DISABLE is displayed, the interface works in non-auto-negotiation mode.
The two interfaces on the local and remote devices must work in the same negotiation mode (auto-negotiation or non-auto-negotiation mode). You can run the negotiation auto command in the interface view to configure an interface to work in auto-negotiation mode. If the fault persists, configure the interface to work in non-auto-negotiation mode, and forcibly set the same rate and duplex mode for the interconnected interfaces.

- Check the Speed field. If the rates of the interfaces on the local and remote devices are different, run the speed command in the interface view to set the same rate for the two interfaces.
- Check the Duplex field. If the duplex modes of the interfaces on the local and remote devices are different, run the duplex command in the interface view to set the same duplex mode for the two interfaces.
5. Perform a loopback test on the AC using an Ethernet cable to connect the interface to another interface.
If the interface can go Up, the WLAN is working properly. The remote device may be faulty. Contact the vendor of the remote device to rectify the fault.
- If an electrical interface or a combo interface working in electrical mode cannot go Up, change it to another interface. If an optical interface or a combo interface working in optical mode cannot go Up, replace the optical module.

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