3Com WX3000 operation manual Link Aggregation Configuration, Introduction to Link Aggregation

1 Link Aggregation Configuration

zThe term switch used throughout this chapter refers to a switching device in a generic sense or the switching engine of a unified switch in the WX3000 series.

zThe sample output information in this manual was created on the WX3024. The output information on your device may vary.

Overview

Introduction to Link Aggregation

Link aggregation means aggregating several ports together to form an aggregation group, so as to implement outgoing/incoming load sharing among the member ports in the group and to enhance the connection reliability.

Depending on different aggregation modes, link aggregation falls into three types: manual, static LACP, and dynamic LACP aggregations. Depending on whether or not load sharing is implemented, aggregation groups can be load-sharing or non-load-sharing aggregation groups.

For the member ports in an aggregation group, their basic configuration must be the same. The basic configuration includes STP, QoS, VLAN, port attributes and other associated settings.

zSTP configuration, including STP status (enabled or disabled), link attribute (point-to-point or not), STP priority, path cost, standard packet format, maximum packet transmission speed, loop prevention status, root protection status, edge port or not.

zQoS configuration, including traffic limit, priority remarking, default 802.1p priority, bandwidth assurance, congestion avoidance, traffic redirection, traffic statistics, and so on.

zVLAN configuration, including permitted VLANs, and default VLAN ID.

zPort attribute configuration, including port rate, duplex mode, and link type (trunk, hybrid, or access).

Introduction to LACP

The purpose of link aggregation control protocol (LACP) is to implement dynamic link aggregation and deaggregation. This protocol is based on IEEE802.3ad and uses LACPDUs (link aggregation control protocol data unit) to interact with its peer.

After LACP is 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.

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