Cisco 350 Series Administration Manual page 242

Port Management
Green Ethernet
NOTE
Cisco 350, 350X and 550X Series Managed Switches, Firmware Release 2.4, ver 0.4
802.3az Energy Efficient Ethernet Feature
This section describes the 802.3az Energy Efficient Ethernet (EEE) feature.
It covers the following topics:
• 802.3az EEE Overview
• Advertise Capabilities Negotiation
• Link Level Discovery for 802.3az EEE
• Availability of 802.3az EEE
• Default Configuration
• Interactions Between Features
• 802.3az EEE Configuration Workflow
802.3az EEE Overview
802.3az EEE is designed to save power when there is no traffic on the link. In Green Ethernet,
power is reduced when the port is down. With 802.3az EEE, power is reduced when the port is
up, but there is no traffic on it.
802.3az EEE is not supported on the Out Of Band port.
The remote link partner status can be displayed only when the link speed is 1G or 10G.
When using 802.3az EEE, systems on both sides of the link can disable portions of their
functionality and save power during periods of no traffic.
802.3az EEE supports IEEE 802.3 MAC operation at 100 Mbps and 1000 Mbps:
LLDP is used to select the optimal set of parameters for both devices. If LLDP is not
supported by the link partner, or is disabled, 802.3az EEE still be operational, but it might not
be in the optimal operational mode.
The 802.3az EEE feature is implemented using a port mode called Low Power Idle (LPI)
mode. When there is no traffic and this feature is enabled on the port, the port is placed in the
LPI mode, which reduces power consumption dramatically.
Both sides of a connection (device port and connecting device) must support 802.3az EEE for
it to work. When traffic is absent, both sides send signals indicating that power is about to be
reduced. When signals from both sides are received, the Keep Alive signal indicates that the
ports are in LPI status (and not in Down status), and power is reduced.
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