Duplex - Cisco Catalyst 2950 Command Reference Manual

duplex

duplex
Use the duplex interface configuration command to specify the duplex mode of operation for the switch
ports. Use the no form of this command to return to the default setting.
Syntax Description
auto
full
half
Defaults For Fast Ethernet and 10/100/1000 ports, the default is auto.
For the default duplex mode of the Gigabit Interface Converter (GBIC)-module ports, see the
documentation that came with your GBIC module.
For small, form-factor pluggable (SFP) Gigabit Ethernet ports on Catalyst 2950 LRE switches, the
default is auto.
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.
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.
Beginning with Cisco IOS Release 12.1(22)EA1, you can configure the duplex setting when the speed
is set to auto.
If both the speed and duplex are set to specific values, autonegotiation is disabled.
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.
The 100BASE-FX ports on Catalyst 2950C-24 switches do not support the duplex interface
configuration command. These ports only operate in full-duplex and at 100 Mbps.
You can configure the 10/100/1000 ports on the Catalyst 2950T-24 and Catalyst 2950T-48-SI switches
to autonegotiate the duplex mode by using the duplex auto interface configuration command. You can
manually set the duplex mode to full by using the duplex full command. The 10/100/1000 ports support
the half keyword only when the interface speed is 10 or 100 Mbps.
Catalyst 2950 and Catalyst 2955 Switch Command Reference
2-108
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 introduced.
Chapter 2 Catalyst 2950 and 2955 Cisco IOS Commands
OL-10102-01