Configuring Ethernet Interfaces
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Changing the interface speed and duplex mode configuration might shut down and re-enable the
Caution
interface during the reconfiguration.
Setting the Interface Speed and Duplex Parameters
To set the speed and duplex mode for a physical interface, follow these steps beginning in privileged EXEC
mode:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
speed {10 | 100 | 1000 | auto [10 | 100 |
1000] | nonegotiate}
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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The 1000BASE-T SFP module ports support the same speed and duplex options as the
–
10/100/1000-Mb/s ports.
For information about which SFP modules are supported on your switch, see the product release
notes.
If both ends of the line support autonegotiation, we highly recommend the default setting of auto
negotiation.
If one interface supports autonegotiation and the other end does not, configure duplex and speed on
both interfaces; do not use the auto setting on the supported side.
When STP is enabled and a port is reconfigured, the switch can take up to 30 seconds to check for
loops. The port LED is amber while STP reconfigures.
Purpose
Enters global configuration mode.
Specifies the physical interface to be configured, and enter interface
configuration mode.
This command is not available on a 10-Gigabit Ethernet interface.
Enters the appropriate speed parameter for the interface:
Enter 10, 100, or 1000 to set a specific speed for the interface.
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The 1000 keyword is available only for 10/100/1000 Mb/s ports.
Enter auto to enable the interface to autonegotiate speed with the
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connected device. If you use the 10, 100, or the 1000 keywords
with the auto keyword, the port autonegotiates only at the
specified speeds.
The nonegotiate keyword is available only for SFP module ports.
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SFP module ports operate only at 1000 Mb/s but can be
configured to not negotiate if connected to a device that does not
support autonegotiation.
For more information about speed settings, see the
Configuration Guidelines" section on page
Chapter 1
Configuring Interface Characteristics
"Speed and Duplex
1-31.
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