Symptom/Cause | Solution |
|---|---|
No cable connected. | Connect cable from switch to a known good device. |
Wrong Port | Make sure that both ends of the cable are plugged into the correct ports. |
Device has no power | Ensure that both devices have power. |
Wrong cable type | Verify the cable selection. |
Bad cable | Swap suspect cable with known good cable. Look for broken or missing pins on connectors. |
Loose connection | Check for loose connections. Sometimes a cable appears to be seated in the jack, but is not. Unplug the cable and reinsert it. |
Patch Panels | Bypass the patch panel if possible to rule it out. |
Media Convertors | Bypass the media convertor (e.g fiber-to-copper) if possible to rule it out. |
Symptom/Cause | Solution |
Bad Port or Module Port or Interface or Module not enabled | Move the cable to a known good port to troubleshoot a suspect port or module. |
Interface is down | Use this command: show interface brief Look for “Status” and “Reason”. If the “Status” is down and “Reason” is AD (Administratively Down), it means that the administrator has disabled the interface. Bring the interface up: no shutdown |
VLAN interface is down | Use these commands: show interface brief Check if the corresponding VLAN interface “Status” is up or down. Also check the value in the “Reason” column. show vlan brief Check if the “State” field to see if it is in “SUSPEND”. Enable the van: vlan <vlan-name> bridge <bridge-id> state enable” Possible cause might be no switchport given on the interface attached to VLAN due to which van is detached from the interface. Enable switchport on that particular interface and attach the van and bridge again. show running-config interface <interface-name> View the configuration. |