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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-21521-01
Chapter 13 Configuring Interface Characteristics
Configuring Ethernet Interfaces
Configuring Interface Speed and Duplex Mode
Ethernet interfaces on the switch operate at 10, 100, 1000, or 10,000 Mb/s and in either full- or
half-duplex mode. In full-duplex mode, two stations can send and receive traffic at the same time.
Normally, 10-Mb/s ports operate in half-duplex mode, which means that stations can either receive or
send traffic.
Switch models include Gigabit Ethernet (10/100/1000-Mb/s) ports, 10-Gigabit Ethernet ports, and small
form-factor pluggable (SFP) module slots supporting SFP modules.
These sections describe how to configure the interface speed and duplex mode:
• Speed and Duplex Configuration Guidelines, page 13-28
• Setting the Interface Speed and Duplex Parameters, page 13-29

Speed and Duplex Configuration Guidelines

When configuring an interface speed and duplex mode, note these guidelines:
• The 10-Gigabit Ethernet ports do not support the speed and duplex features. These ports operate
only at 10,000 Mb/s and in full-duplex mode.
• Gigabit Ethernet (10/100/1000-Mb/s) ports support all speed options and all duplex options (auto,
half, and full). However, Gigabit Ethernet ports operating at 1000 Mb/s do not support half-duplex
mode.
• For SFP module ports, the speed and duplex CLI options change depending on the SFP module type:
–
The 1000BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support
the nonegotiate keyword in the speed interface configuration command. Duplex options are not
supported.
–
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.
Auto-MDIX Enabled.
Note The switch might not support a pre-standard powered device—such as
Cisco IP phones and access points that do not fully support IEEE
802.3af—if that powered device is connected to the switch through a
crossover cable. This is regardless of whether auto-MIDX is enabled on
the switch port.
Power over Ethernet (PoE) Enabled (auto).
Table 13-3 Default Layer 2 Ethernet Interface Configuration (continued)
Feature Default Setting