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Cisco ME 3400E Ethernet Access Switch Hardware Installation Guide
OL-16447-01
Appendix 4 Troubleshooting
Clearing the Switch IP Address and Configuration

Switch Performance

Speed, Duplex, and Autonegotiation

If the port statistics show a large amount of alignment errors, frame check sequence (FCS), or
late-collisions errors, this might mean a speed or duplex mismatch.
A common issue with speed and duplex is when the duplex settings are mismatched between two
switches, between a switch and a router, or between the switch and a workstation or server. Mismatches
can happen when manually setting the speed and duplex or from autonegotiation issues between the two
devices.
To maximize switch performance and to ensure a link, follow one of these guidelines when changing the
duplex or speed settings.
• 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, set the same duplex settings on the two ports. The speed
parameter adjusts itself even if the connected port does not autonegotiate.

Autonegotiation and NICs

Problems sometimes occur between the switch and third-party network interface cards (NICs). By
default, the switch ports and interfaces are set to autonegotiate. Devices like laptops or other devices are
commonly set to autonegotiate, yet sometimes autonegotation issues occur.
To troubleshoot autonegotiation problems, try manually setting both sides of the connection. If this does
not solve the problem, there could be a problem with the firmware or software on your NIC. You can
resolve this by upgrading the NIC driver to the latest available version.

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 “Cables and
Adapters” section on page B-4 for cabling guidelines.
Clearing the Switch IP Address and Configuration
This section describes how to reset the switch by rerunning the initial configuration dialog (system
configuration dialog). These are reasons why you might want to reset the switch:
• You installed the switch in your network and cannot connect to it because you assigned the wrong
IP address.
• You want to clear all the configuration settings from the switch and assign a new IP address.
Caution This procedure clears the IP address and all configuration information stored on the switch. Do not
follow this procedure unless you want to completely reconfigure the switch.