Chapter 12
Configuring Interface Characteristics
The switch does not have this behavior with 100BASE-FX-GE SFP modules.
Configuring 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 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 can include combinations of Fast Ethernet (10/100-Mb/s) ports, Gigabit Ethernet
(10/100/1000-Mb/s) ports, 10-Gigabit module ports, and small form-factor pluggable (SFP) module
slots supporting SFP modules.
These sections describe how to configure the interface speed and duplex mode:
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Speed and Duplex Configuration Guidelines
When configuring an interface speed and duplex mode, note these guidelines:
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Changing the interface speed and duplex mode configuration might shut down and re-enable the
Caution
interface during the reconfiguration.
OL-26520-01
Speed and Duplex Configuration Guidelines, page 12-29
Setting the Interface Speed and Duplex Parameters, page 12-30
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
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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
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10/100/1000-Mb/s ports.
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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 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.
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
Configuring Ethernet Interfaces
12-29