Cisco Systems WSC3750X24TS Monitor Switch Performance, Speed, Duplex, and Autonegotiation

Chapter 3 Troubleshooting

Diagnosing Problems

Monitor Switch Performance

Review this section when you troubleshoot switch performance problems.

Speed, Duplex, and Autonegotiation

If the port statistics show a large number of alignment errors, frame check sequence (FCS), or late-collisions errors, a speed or duplex mismatch might be the problem.

A common issue with speed and duplex occurs when the duplex settings are mismatched between two switches, between a switch and a router, or between the switch and a workstation or server. This can happen when you manually set the speed and duplex or because of autonegotiation issues between the two devices.

These circumstances can result in a mismatch:

•A manually set speed or duplex parameter is different from the manually set speed or duplex parameter on the connected port.

•A port is set to autonegotiate, and the connected port is set to full duplex with no autonegotiation.

To maximize switch performance and to ensure a link, follow one of these guidelines when you set or change the settings for duplex and speed:

•Let both ports autonegotiate both speed and duplex.

•Manually set the speed and duplex parameters for the ports on both ends of the connection.

•If a remote device does not autonegotiate, configure the duplex settings on the two ports to match. The speed parameter can adjust itself even if the connected port does not autonegotiate.

Autonegotiation and NIC Cards

Problems sometimes occur between the switch and third-party network interface cards (NICs). By default, the switch ports and interfaces are set to autonegotiate. It is common for devices such as laptop computers or other devices to also be set to autonegotiate, yet sometimes autonegotation issues occur.

To troubleshoot autonegotiation problems, try to manually set both sides of the connection. If this does not solve the problem, the firmware or software on your NIC card might be causing the problem. Upgrade the NIC card driver to the latest version available from the manufacturer.

Cabling Distance

If the port statistics show excessive FCS, late-collision, or alignment errors, verify that the cable distance from the switch to the connected device meets the recommended guidelines. See the “Cable and Adapter Specifications” section on page A-4for cabling guidelines.

Catalyst 3750 Switch Hardware Installation Guide

OL-6336-07 3-5