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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 15 Configuring Interface Characteristics
Information About Configuring Interface Characteristics
Interface Speed and Duplex Mode
Depending on the supported port types, Ethernet interfaces on the switch operate at 10, 100, or 1000
Mb/s, or 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 can include combinations of Fast Ethernet (10/100-Mb/s) ports, Gigabit Ethernet
(10/100/1000-Mb/s) ports, and small form-factor pluggable (SFP) module slots supporting SFP
modules.

Speed and Duplex Configuration Guidelines

When configuring an interface speed and duplex mode, note these guidelines:
Fast Ethernet (10/100-Mb/s) ports support all speed and duplex options.
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.
The 100BASE-x (where -x is -BX, -CWDM, -LX, -SX, and -ZX) SFP module ports support only
100 Mb/s. These modules support full- and half- duplex opti ons 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 reenable the interface
during the reconfiguration.
IEEE 802.3x Flow Control
Flow control enables connected Ethernet ports to control traffic rates during congestion by allowing
congested nodes to pause link operation at the other end. If one port experiences congestion and ca nnot
receive any more traffic, it notifies the other port by sending a pause frame to stop sending until the
condition clears. Upon receipt of a pause frame, the sending device stops sending any data packets,
which prevents any loss of data packets during the congestion period.