5-5
Catalyst 3650 Switch Hardware Installation Guide
OL-29734-01
Chapter 5 Troubleshooting
Resetting the Switch
Switch Performance
The following are some of the scenarios relating to switch performance that might require
troubleshooting.
Speed, Duplex, and Autonegotiation
Port statistics that show a large amount of alignment errors, frame check sequences (FCS), or
late-collisions errors, might indicate a speed or duplex mismatch.
A common issue occurs when duplex and speed settings are mismatched between two switches, between
a switch and a router, or between a switch and a workstation or server. Mismatches might occur 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 the ports autonegotiate both the speed and the duplex.
•
Manually set the speed and duplex parameters for the interfaces on both ends of the connection.
•
If a remote device does not autonegotiate, use the same duplex settings on the two ports. The speed
parameter adjusts itself even if the connected port does not autonegotiate.
Autonegotiation and Network Interface Cards
Sometimes, problems occur between the switch and third-party network interface cards (NICs). By
default, the switch ports and interfaces autonegotiate. Laptops or other devices are commonly set to
autonegotiate; yet, sometimes, issues occur.
To troubleshoot autonegotiation problems, try setting both sides of the connection manually. If this does
not solve the problem, there could be a problem with the firmware or software on the NIC. You can
resolve this by upgrading the NIC driver to the latest version.
Cabling Distance
If the port statistics show excessive frame check sequences, late-collisions or alignment errors, verify
that the cable distance from the switch to the connected device meets the recommended guidelines..
Resetting the Switch
If you have configured a new switch with a wrong IP address, or if all of the switch LEDs start blinking
when you try to enter Express Setup mode, you can clear the IP address that is configured on the switch.
Note
Resetting the switch reboots the switch.
To reset the switch
Step 1
Press and hold the
Mode
button.