Specifications

9-10
Catalyst 2970 Switch Software Configuration Guide
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Chapter 9 Configuring Interface Characteristics
Configuring Ethernet Interfaces
Configuring Interface Speed and Duplex Mode
Ethernet interfaces on the switch operate at 10, 100, or 1000 Mbps 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-Mbps ports operate in half-duplex mode, which means that stations can either receive or send traffic.
Switch models include Gigabit Ethernet (10/100/1000-Mbps) ports and small form-factor pluggable
(SFP) module slots supporting Gigabit SFP modules.
• You can configure interface speed on Gigabit Ethernet (10/100/1000-Mbps) interfaces. You can
configure Gigabit Ethernet interfaces to full-duplex mode or to autonegotiate; you cannot configure
half-duplex mode on Gigabit Ethernet ports.
• You cannot configure speed or duplex mode on most SFP ports, but you can configure speed to not
negotiate (nonegotiate) if connected to a device that does not support autonegotiation. However,
when a 1000BASE-T SFP module is in the SFP module port, you can configure speed as 10, 100, or
1000 Mbps, and you can configure duplex mode to auto or full.
These sections describe how to configure the interface speed and duplex mode:
• Configuration Guidelines, page 9-10
• Setting the Interface Speed and Duplex Parameters, page 9-11
Configuration Guidelines
When configuring an interface speed and duplex mode, note these guidelines:
• 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.
• For 10/100/1000 Mbps ports, if both the speed and duplex mode are set to specific values,
autonegotiation is disabled.
• You cannot configure duplex mode on SFP module ports; they operate in full-duplex mode.
However, when a 1000BASE-T SFP module is inserted in an SFP module port, you can configure
the duplex mode to full or auto and half-duplex mode is supported with the auto configuration.
• You cannot configure speed on SFP module ports, except to nonegotiate. However, when a
1000BASE-T SFP module is in the SFP module port, the speed can be configured to 10, 100, 1000,
or auto, but not nonegotiate.
Port Fast Disabled.
Auto-MDIX Disabled.
Note The switch might not support a pre-standard power
device—such as Cisco IP phones and access points that do
not fully support IEEE 802.3AF—if that power device is
connected to the switch through a crossover cable. This is
regardless of whether Auto-MIDX is enabled on the
switch port.
Table 9-1 Default Layer 2 Ethernet Interface Configuration (continued)
Feature Default Setting