C
HAPTER
29
| Interface Commands
Power Savings
– 978 –
EXAMPLE
Console#show cable-diagnostics interface ethernet 1/24
Port Type Link Status Pair A (meters) Pair B (meters) Last Update
-------- ---- ----------- ---------------- ---------------- -------------------
Eth 1/24 GE Up OK (1) OK (1) 2012-08-09 10:24:49
Console#
Power Savings
power-save This command enables power savings mode on the specified port. Use the
no form to disable this feature.
SYNTAX
[no] power-save
DEFAULT SETTING
Enabled
COMMAND MODE
Interface Configuration (Ethernet)
COMMAND USAGE
u IEEE 802.3 defines the Ethernet standard and subsequent power
requirements based on cable connections operating at 100 meters.
Enabling power saving mode can reduce power used for cable lengths
of 60 meters or less, with more significant reduction for cables of 20
meters or less, and continue to ensure signal integrity.
u Power saving mode only applies to the Gigabit Ethernet ports using
copper media.
u Power savings can be enabled on Gigabit Ethernet RJ-45 ports.
u The power-saving methods provided by this switch include:
n
Power saving when there is no link partner:
Under normal operation, the switch continuously auto-negotiates to
find a link partner, keeping the MAC interface powered up even if no
link connection exists. When using power-savings mode, the switch
checks for energy on the circuit to determine if there is a link
partner. If none is detected, the switch automatically turns off the
transmitter, and most of the receive circuitry (enters Sleep Mode).
In this mode, the low-power energy-detection circuit continuously
checks for energy on the cable. If none is detected, the MAC
interface is also powered down to save additional energy. If energy
is detected, the switch immediately turns on both the transmitter
and receiver functions, and powers up the MAC interface.
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