Duplex - Cisco Catalyst 2950 Command Reference Manual

duplex

duplex
Use the duplex interface configuration command to specify the duplex mode of operation for switch
ports. Use the no form of this command to return the port to its default value.
Syntax Description
auto
full
half
Defaults
For Fast Ethernet and 10/100/1000 ports, the default is auto.
For 100BASE-FX ports, the default is full.
For the default duplex mode of the Gigabit Interface Converter (GBIC)-module ports, refer to the
documentation that came with your GBIC module.
Command Modes Interface configuration
Command History Release
12.0(5.2)WC(1)
Usage Guidelines Certain ports, such as GBIC module ports, can be configured to be either full duplex or half duplex. The
applicability of this command depends on the device to which the switch is attached.
The 100BASE-FX ports on Catalyst 2950C-24 switches do not support the duplex command. These
ports only operate in full-duplex and 100-Mbps mode.
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.
If the speed is set to auto, the switch negotiates with the device at the other end of the link for the speed
setting and then forces the speed setting to the negotiated value. The duplex setting remains as
configured on each end of the link, which could result in a duplex setting mismatch.
The 10/100/1000 ports can operate only in the full-duplex mode.
Note
If both the speed and duplex are set to specific values, autonegotiation is disabled.
Note For guidelines on setting the switch speed and duplex parameters, refer to the Catalyst 2950 Desktop
Switch Hardware Installation Guide.
Catalyst 2950 Desktop Switch Command Reference
2-54
duplex {auto | full | half}
no duplex
Port automatically detects whether it should run in full- or half-duplex mode.
Port is in full-duplex mode.
Port is in half-duplex mode.
Modification
This command was first introduced.
Chapter 2 Cisco IOS Commands
78-11381-05