Configuring link aggregation and lacp, Overview, Basic concepts of link aggregation – H3C Technologies H3C WX5500E Series Access Controllers User Manual
Page 200: 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.
Basic concepts of link aggregation
Aggregate interface
An aggregate interface is a logical Layer 2 or Layer 3 aggregate 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, depending on the following aggregate
interface types:
•
If the aggregate interface is a Layer 2 interface, a Layer 2 aggregation group is created. You can
assign only Layer 2 Ethernet interfaces to the group.
•
If the aggregate interface is a Layer 3 interface, a Layer 3 aggregation group is created. You can
assign only Layer 3 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. For information about
dynamic aggregation groups, see "
." 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 to determine the interfaces that