Duplex - Cisco Catalyst 3750 Command Reference Manual

Chapter 2 Catalyst 3750 Switch Cisco IOS Commands

duplex

Use the duplex interface configuration command on the switch stack or on a standalone switch to specify
the duplex mode of operation for Fast Ethernet and Gigabit Ethernet ports. Use the no form of this
command to return the port to its default value.
Syntax Description
auto
full
half
Defaults The default is auto.
Command Modes Interface configuration
Command History Release
12.1(11)AX
Usage Guidelines
This command is not available on small form-factor pluggable (SFP) module ports unless a 1000BASE-T
SFP module is in the port. All other SFP modules operate only in full-duplex mode.
This command is not available on a 10-Gigabit Ethernet interface.
Certain ports can be configured to be either full duplex or half duplex. Applicability of this command
depends on the device to which the switch is attached.
For Fast Ethernet ports, setting the port to auto has the same effect as specifying half if the attached
device does not autonegotiate the duplex parameter.
For Gigabit Ethernet ports, setting the port to auto has the same effect as specifying full if the attached
device does not autonegotiate the duplex parameter.
You cannot configure duplex mode on SFP module interfaces. However, when a 1000BASE-T SFP
module is in the SFP module port, you can configure duplex mode to auto or full.
Note
78-16181-01
duplex {auto | full | half}
no duplex
Enable automatic duplex configuration; port automatically detects whether it
should run in full- or half-duplex mode, depending on the attached device mode.
Enable full-duplex mode.
Enable half-duplex mode (only for interfaces operating at 10 Mbps or 100 Mbps).
You cannot configure half-duplex mode for interfaces operating at 1000 Mbps or
10,000 Mbps.
Modification
This command was introduced.
Half-duplex mode is supported on Gigabit Ethernet interfaces; however , you cannot configure
these interfaces to operate in half-duplex mode.
Catalyst 3750 Switch Command Reference
duplex
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