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3Com Switch 8800 Configuration Guide Chapter 7 Link Aggregation Configuration
7-1
Chapter 7 Link Aggregation Configuration
7.1 Overview
7.1.1 Introduction to Link Aggregation
Link aggregation means aggregating several ports together to implement the
outgoing/incoming payload balance among the member ports and enhance the
connection reliability. Link aggregation may be manual aggregation, dynamic LACP
aggregation or static LACP aggregation. For the member ports in an aggregation group,
their basic configurations must be the same. That is, if one is a trunk port, others must
also be; when it turns into access port, then others must change to access port.
Basic configuration includes STP setting, QoS setting, VLAN setting, and port setting.
The STP setting includes STP enabling/disabling, link attribute (point-to-point or not),
STP priority, path cost, max transmission speed, loop protection, root protection, edge
port or not. The QoS setting includes traffic limiting, priority marking, default 802.1p
priority, bandwidth assurance, congestion avoidance, traffic redirection, traffic statistics.
The VLAN setting includes permitted VLAN types, default VLAN ID. The port setting
includes port link type.
One Switch 8800 can support up to 728 aggregation groups (seven load sharing
aggregation groups at most), with each group containing a maximum of eight ports.
Note:
The Switch 8800 also supports trans-board aggregation. The trans-board aggregation
is the same as the intra-board aggregation.
7.1.2 Introduction to LACP
Link aggregation control protocol (LACP) based on the IEEE802.3ad standard can be
used in dynamic link aggregation. An LACP-enabled port sends link aggregation
control protocol data units (LACPDUs) to tell the peer about its system priority, system
MAC address, port priority, port number and operation key. After receiving the
information from the sender, the receiver compares it with the locally saved information
about other ports, chooses member ports for the aggregation group and reaches
agreement about if a port can join or leave a dynamic aggregation group.
During port aggregation, LACP generates a configuration mix according to the port
configuration (rate, duplex, basic configuration, management key), which is called an