A loopback test helps determine whether the issue is related to the SFP module, the switch port, or the external fiber cable. Procedure: Connect the Tx (transmit) and Rx (receive) ports using a loopback cable. Before you blame the switch or replace the cable, you need to look at the invisible data: the light levels. The table describes the LED status indicators for Ethernet modules or fixed-configuration switches: Ensure that both sides have. This article provides instructions on how to view the Optical Module Status on your switch through the Command Line Interface (CLI). The status LEDs can display solid amber or flash during boot, POST, or other diagnostic tests. Flashing lights may be slow, fast, or flickering. The LED colors are either green or amber. Status UP indicates normal link connection.
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