Ethernet Link Aggregation Configuration; Overview; Basic Concepts - H3C S5120-EI Configuration Manual

Ethernet link aggregation configuration

Overview

Ethernet link aggregation, or simply link aggregation, combines multiple physical Ethernet ports into one
logical link, called an "aggregate link". Link aggregation delivers the following benefits:
Increases bandwidth beyond the limits of any single link. In an aggregate link, traffic is distributed
•
across the member ports.
• Improves link reliability. The member ports dynamically back up one another. When a member port
fails, its traffic is automatically switched to other member ports.
As shown in
physical Ethernet links are combined into an aggregate link, Link Aggregation 1. The bandwidth of this
aggregate link is as high as the total bandwidth of the three physical Ethernet links. At the same time, the
three Ethernet links back up one another.
Figure 8 Ethernet link aggregation

Basic concepts

Aggregation group, member port, aggregate interface
Link aggregation is implemented through link aggregation groups. An aggregation group is a group of
Ethernet interfaces combined together, which are called "member ports" of the aggregation group. For
each aggregation group, a logical interface, called an "aggregate interface", is created.
NOTE:
The rate of an aggregate interface equals the total rate of its member ports in the Selected state, and its
duplex mode is the same as the selected member ports. For more information about the states of member
ports in an aggregation group, see
Aggregation states of member ports in an aggregation group
A member port in an aggregation group can be in either of the following aggregation states:
Selected: A Selected port can forward user traffic.
•
• Unselected: An Unselected port cannot forward user traffic.
Operational key
When aggregating ports, the system automatically assigns each port an operational key based on port
information such as port rate and duplex mode. Any change to this information triggers a recalculation
of the operational key.
In an aggregation group, all selected member ports are assigned the same operational key.
Figure 8, Device A and Device B are connected by three physical Ethernet links. These
"Aggregation states of member ports in an aggregation
31
group."