Switch Performance - Cisco Catalyst IE3400 Heavy Duty Series Installation Manual

10/100 and 10/100/1000 Port Connections
• Make sure that both ends of the cable are connected to the correct ports.
• Verify that both devices have power.
• Verify that you are using the correct cable type.
• Look for loose connections. Sometimes a cable appears to be seated but is not. Disconnect the cable, and
10/100 and 10/100/1000 Port Connections
If a port appears to malfunction:
• Verify the status of all ports. See
• Use the show interfaces privileged EXEC command to see if the port is error-disabled, disabled, or shut
• Verify the cable type.
Interface Settings
Verify that the interface is not disabled or powered off. If an interface is manually shut down on either side
of the link, it does not come up until you reenable the interface. Use the show interfaces privileged EXEC
command to see if the interface is error-disabled, disabled, or shut down on either side of the connection. If
needed, reenable the interface.
Ping End Device
Ping from the directly connected switch first, and then work your way back port by port, interface by interface,
trunk by trunk, until you find the source of the connectivity issue. Make sure that each switch can identify
the end device MAC address in its Content-Addressable Memory (CAM) table.
Spanning Tree Loops
STP loops can cause serious performance issues that look like port or interface problems.
A unidirectional link can cause loops. It occurs when the traffic sent by the switch is received by the neighbor,
but notification that the traffic was received from the neighbor is not received by the switch. A broken cable,
other cabling problems, or a port issue can cause this one-way communication.
You can enable UniDirectional Link Detection (UDLD) on the switch to help identify unidirectional link
problems. For information about enabling UDLD on the switch, see the "Information About UDLD" section
in the

Switch Performance

Speed, Duplex, and Autonegotiation
Port statistics that show a large amount of alignment errors, frame check sequence (FCS), or late-collisions
errors, a common issue when duplex and speed settings are mismatched between two devices.
To maximize switch performance and to ensure a link, follow one of these guidelines when changing the
duplex or the speed settings.
• Let both ports autonegotiate both speed and duplex.
Cisco Catalyst IE3400 Heavy Duty Series Hardware Installation Guide
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then reconnect it.
down. Reenable the port if necessary.
IOS-XE Software Configuration guide for the Cisco Catalyst IE 3x00
Table 1-1 for descriptions of the LEDs and their meanings.
Troubleshooting
Switches, on Cisco.com.