User manual

Publication 1783-UM003D-EN-E - December 2009 145
Chapter 5
Issue Resolution
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 indicate a speed or duplex mismatch.
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 manually setting the speed and duplex or from
autonegotiation issues between the two devices. A mismatch occurs under these
circumstances:
• 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 ensure a link, follow one of these guidelines when
changing the settings for duplex and speed:
• Let both ports autonegotiate both speed and duplex.
• Manually set the same speed and duplex parameters for the ports on both ends of the
connection to the same values.
• If a remote device does not autonegotiate, configure the duplex settings on the two
ports to the same values.
The speed parameter can adjust itself even if the connected port does not
autonegotiate.
Autonegotiation and Network Interface
Cards (NICs)
Issues 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 like laptops or other devices to be set to autonegotiate as well, yet sometimes
autonegotiation issues occur.
To troubleshoot autonegotiation issues, try manually setting both sides of the connection. If
this does not solve the issue, there could be an issue with the firmware or software on your
NIC. You can resolve this by upgrading the NIC 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.