11-18
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 11 Configuring Interface Characteristics
Configuring Ethernet Interfaces
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The 100BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support only
100 Mbps. These modules support full- and half- duplex options but do not support
autonegotiation.
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.
Caution Changing the interface speed and duplex mode configuration might shut down and re-enable the
interface during the reconfiguration.
Setting the Interface Speed and Duplex Parameters
Beginning in privileged EXEC mode, follow these steps to set the speed and duplex mode for a physical
interface:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Specify the physical interface to be configured, and enter interface
configuration mode.
Step 3
speed {10 | 100 | 1000 | auto [10 | 100 |
1000] | nonegotiate}
This command is not available on a 10-Gigabit Ethernet interface.
Enter the appropriate speed parameter for the interface:
• Enter 10, 100, or 1000 to set a specific speed for the interface.
The 1000 keyword is available only for 10/100/1000 Mbps ports.
• Enter auto to enable the interface to autonegotiate speed with the
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.
SFP module ports operate only at 1000 Mbps 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 “Speed and Duplex
Configuration Guidelines” section on page 11-17.
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