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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
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Chapter 6 Configuring Interfaces
Configuring Optional Interface Features
Setting the Ethernet Interface Speed
Note If you set the Ethernet port speed to auto on a 10/100-Mbps or 10/100/1000-Mbps Ethernet port, both
speed and duplex are autonegotiated.
To set the port speed for a 10/100 or a 10/100/1000-Mbps Ethernet port, perform this task:
This example shows how to set the speed to 100 Mbps on the Fast Ethernet port 5/4:
Router(config)# interface fastethernet 5/4
Router(config-if)# speed 100
Setting the Interface Duplex Mode
Note 10-Gigabit Ethernet and Gigabit Ethernet are full duplex only. You cannot change the duplex mode
on 10-Gigabit Ethernet or Gigabit Ethernet ports or on a 10/100/1000-Mps port configured for
Gigabit Ethernet.
If you set the port speed to auto on a 10/100-Mbps or a 10/100/1000-Mbps Ethernet port, both speed
and duplex are autonegotiated. You cannot change the duplex mode of autonegotiation ports.
To set the duplex mode of an Ethernet or Fast Ethernet port, perform this task:
This example shows how to set the duplex mode to full on Fast Ethernet port 5/4:
Router(config)# interface fastethernet 5/4
Router(config-if)# duplex full
Configuring Link Negotiation on Gigabit Ethernet Ports
Note Link negotiation does not negotiate port speed.
On Gigabit Ethernet ports, link negotiation exchanges flow-control parameters, remote fault
information, and duplex information. Link negotiation is enabled by default.
Command Purpose
Step 1 Router(config)# interface fastethernet slot/port Selects the Ethernet port to be configured.
Step 2 Router(config-if)# speed {10 | 100 | 1000 | auto} Sets the speed of the Ethernet interface.
Router(config-if)# no speed Reverts to the default configuration (speed auto).
Command Purpose
Step 1 Router(config)# interface fastethernet slot/port Selects the Ethernet port to be configured.
Step 2 Router(config-if)# duplex [auto | full | half] Sets the duplex mode of the Ethernet port.
Router(config-if)# no duplex Reverts to the default configuration (duplex auto).