12-19
Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 12 Configuring Interface Characteristics
Configuring Ethernet Interfaces
The switch operates with 100BASE-
x
(where -
x
is -BX, -FX-FE, -LX) SFP modules as follows:
•
When the 100BASE -
x
SFP module is inserted into the module slot and there is no link on the RJ-45
side, the switch disables the RJ-45 interface and selects the SFP module interface. This is the
behavior even if there is no cable connected and if there is no link on the SFP module side.
•
When the 100BASE-
x
SFP module is inserted and there is a link on the RJ-45 side, the switch
continues with that link. If the link goes down, the switch disables the RJ-45 side and selects the
SFP module interface.
•
When the 100BASE-
x
SFP module is removed, the switch again dynamically selects the type
(
auto-select
) and re-enables the RJ-45 side.
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:
•
Speed and Duplex Configuration Guidelines, page 12-19
•
Setting the Interface Speed and Duplex Parameters, page 12-20
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 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.