Setting The Interface Speed - Cisco Catalyst 4500 Series Software Configuration Manual

On a Catalyst 4500-X switch, the duplex mode is always automatically configured as full duplex (whether you set the
interface speed to 10 or 100). You cannot change this.
Changing the interface speed and duplex mode configuration might shut down and restart the interface
Caution
during the reconfiguration.

Setting the Interface Speed

If you set the interface speed to auto on a 10/100-Mbps Ethernet interface, speed and duplex are autonegotiated. The forced
10/100 autonegotiation feature allows you to limit interface speed auto negotiation up to 100 Mbps on a 10/100/1000BASE-T
port.
To set the port speed for a 10/100-Mbps Ethernet interface, perform this task:
Command
Step 1
Switch(config)# interface fastethernet slot/interface
Step 2
Switch(config-if)# speed [10 | 100 | auto [10 | 100]]
This example shows how to set the interface speed to 100 Mbps on the Fast Ethernet interface 5/4:
Switch(config)# interface fastethernet 5/4
Switch(config-if)# speed 100
This example shows how to allow Fast Ethernet interface 5/4 to autonegotiate the speed and duplex mode:
Switch(config)# interface fastethernet 5/4
Switch(config-if)# speed auto
The preceding CLI is analogous to speed auto 10 100.
Note
This example shows how to limit the interface speed to 10 and 100 Mbps on the Gigabit Ethernet interface 1/1 in
auto-negotiation mode:
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# speed auto 10 100
This example shows how to limit speed negotiation to 100 Mbps on the Gigabit Ethernet interface 1/1:
Switch(config)# interface gigabitethernet 1/1
Switch(config-if)# speed auto 100
Turning off autonegotiation on a Gigabit Ethernet interface results in the port being forced into
Note
1000 Mbps and full-duplex mode.
To turn off the port speed autonegotiation for Gigabit Ethernet interface 1/1, perform this task:
Command
Step 1
Switch(config)# interface gigabitethernet1/1
Step 2
Switch(config-if)# speed nonegotiate
To restore autonegotiation, enter the no speed nonegotiate command in the interface configuration mode.
Configuring Optional Interface Features
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS
9
Purpose
Specifies the interface to be configured.
Sets the interface speed.
Purpose
Specifies the interface to be configured.
Disables autonegotiation on the interface.
Chapter 9 Configuring Interfaces