If the link light for the port does not come on, you can consider these possibilities: Possible CauseĬonnect cable from switch to a known good device. Check the Cable and Both Sides of the Connection Normally you can identify this situation if the port has many packet errors, or the port constantly flaps (loses and regains link). The cable can have encountered physical stress that causes it to be functional at a marginal level. A single broken wire or one shutdown port can cause the problem where one side has a link light, but the other side does not.Ī link light does not guarantee that the cable is fully functional.

The table describes the LED status indicators for Ethernet modules or fixed-configuration switches: PlatformĮnsure that both sides have a link. If you have physical access to the switch, it can save time to look at the port LEDs which give you the link status or can indicate an error condition (if red or orange).

Troubleshoot the Physical Layer Use the LEDs to Troubleshoot Note: To access tools and websites, you must be a registered Cisco client. Refer to Cisco Technical Tips Conventionsfor more information on document conventions. If your network is live, ensure that you understand the potential impact of any command. All of the devices used in this document started with a cleared (default) configuration. The information in this document was created from the devices in a specific lab environment. This document applies to Catalyst switches that run on Cisco IOS® System Software. There are no specific requirements for this document. This document describes how to determine why a port or interface experiences problems.

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