Link Aggregation; Overview - 3Com 4210 PWR Configuration Manual

10

Overview

Introduction to Link
Aggregation
Introduction to LACP
Requirements on Ports
for Link Aggregation
L A
INK GGREGATION
Link aggregation can aggregate multiple Ethernet ports together to form a logical
aggregation group. To upper layer entities, all the physical links in an aggregation
group are a single logical link.
Link aggregation is designed to increase bandwidth by implementing
outgoing/incoming load sharing among the member ports in an aggregation
group. Link aggregation group also allows for port redundancy, which improves
connection reliability.
Link aggregation control protocol (LACP) is designed to implement dynamic link
aggregation and deaggregation. This protocol is based on IEEE802.3ad and uses
link aggregation control protocol data units (LACPDUs) to interact with its peer.
With LACP enabled on a port, LACP notifies the following information of the port
to its peer by sending LACPDUs: priority and MAC address of this system, priority,
number and operation key of the port. Upon receiving the information, the peer
compares the information with the information of other ports on the peer device
to determine the ports that can be aggregated. In this way, the two parties can
reach an agreement in adding/removing the port to/from a dynamic aggregation
group.
Operation key is generated by the system. It is determined by port settings such as
port speed, duplex state, basic configuration, and so on.
Selected ports in a manual aggregation group or a static aggregation group
■
have the same operation key.
Member ports in a dynamic aggregation group have the same operation key.
■
To achieve outgoing/incoming load sharing in an aggregation group, the following
configuration of the member ports must be the same: STP, QoS, VLAN, port
attributes, as described below.
STP configuration, including STP status (enabled or disabled), link attribute
■
(point-to-point or not), STP priority, STP path cost, STP packet format, loop
guard status, root guard status, edge port or not.
QoS configuration, including traffic limit, 802.1p priority, and so on.
■
VLAN configuration, including permitted VLANs, and default VLAN ID.
■
Port attribute configuration, including port rate, duplex mode, and link type
■
(trunk, hybrid, or access).
C
ONFIGURATION