Configuring link aggregation and lacp, Overview, Basic concepts of link aggregation – H3C Technologies H3C WX3000E Series Wireless Switches User Manual
Page 240: Aggregate interface, Aggregation group, States of the member ports in an aggregation group, Lacp protocol
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Configuring link aggregation and LACP
Overview
Link aggregation aggregates multiple physical Ethernet ports into one logical link, also called an
aggregation group.
It allows you to increase bandwidth by distributing traffic across the member ports in the aggregation
group. In addition, it provides reliable connectivity because these member ports can dynamically back
up each other.
Support for link aggregation depends on the device model. For more information, see "
Access Controllers Web-Based Configuration Guide
Basic concepts of link aggregation
Aggregate interface
An aggregate interface is a logical interface.
Aggregation group
An aggregation group is a collection of Ethernet interfaces. When you create an aggregate interface, an
aggregation group numbered the same is automatically created.
The creation of a Layer 2 aggregate interface leads to the creation of a Layer 2 aggregation group. You
can assign only Layer 2 Ethernet interfaces to the group.
States of the member ports in an aggregation group
A member port in an aggregation group can be in one of the following states:
•
Selected—A Selected port can forward user traffic.
•
Unselected—An Unselected port cannot forward user traffic.
The rate of an aggregate interface is the sum of the selected member ports' rates. The duplex mode of
an aggregate interface is consistent with that of the selected member ports. All selected member ports
use the same duplex mode.
For information about how to determine the state of a member port, see "
" and
"
LACP protocol
The Link Aggregation Control Protocol (LACP) is defined in IEEE 802.3ad. It uses LACPDUs for
information exchange between LACP-enabled devices.
LACP is automatically enabled on interfaces in a dynamic aggregation group. An LACP-enabled
interface sends LACPDUs to notify the remote system (the partner) of its system LACP priority, system MAC
address, LACP port priority, port number, and operational key. Upon receiving an LACPDU, the partner
compares the received information with the information received on other interfaces, and then
determines the interfaces that can operate as Selected interfaces. This allows the two systems to reach an
agreement on which link aggregation member ports should be placed in Selected state.