Cisco 500 Series Administration Manual page 199

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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.
For ports to stay in LPI mode, the Keep Alive signal must be received continuously
from both sides.
Advertise Capabilities Negotiation
802.3az EEE support is advertised during the Auto-Negotiation stage. Auto-
Negotiation provides a linked device with the capability to detect the abilities
(modes of operation) supported by the device at the other end of the link,
determine common abilities, and configure itself for joint operation. Auto-
Negotiation is performed at the time of link-up, on command from management, or
upon detection of a link error. During the link establishment process, both link
partners to exchange their 802.3az EEE capabilities. Auto-Negotiation functions
automatically without user interaction when it is enabled on the device.
If Auto-Negotiation is not enabled on a port, the EEE is disabled. The
NOTE
only exception is if the link speed is 1GB, then EEE still e enabled even though
Auto-Negotiation is disabled.
Link Level Discovery for
In addition to the capabilities described above, 802.3az EEE capabilities and
settings are also advertised using frames based on the organizationally-specific
TLVs defined in Annex G of IEEE Std 802.1AB protocol (LLDP). LLDP is used to
further optimize 802.3az EEE operation after auto-negotiation is completed. The
802.3az EEE TLV is used to fine tune system wake-up and refresh durations.
Availability of 802.3az EEE
Please see the release notes for a complete listing of products that support EEE.
802.3az
EEE
Cisco 500 Series Stackable Managed Switch Administration Guide
Port Management
Configuring Green Ethernet