Configuring Ethernet Link Aggregation; Overview; Basic Concepts - HP 3100 Series Configuration Manual

Configuring Ethernet link aggregation

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 7 Ethernet link aggregation

Basic concepts

Aggregation group, member port, and aggregate interface
Link aggregation is implemented by combining Ethernet interfaces into a link aggregation group.
Each link aggregation group has one logical aggregate interface. To an upper layer entity that uses
the link aggregation service, a link aggregation group appears to be a single logical link and data
traffic is transmitted through the aggregate interface. 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
Bridge-aggregation (BAGG) interfaces—Also called Layer 2 aggregate interfaces.
When you create an aggregate interface, the switch automatically creates an aggregation group of
the same type and number as the aggregate interface. For example, when you create interface
Bridge-Aggregation 1, Layer 2 aggregation group 1 is automatically created.
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 7, Device A and Device B are connected by three physical Ethernet links. These
group."
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