Configuring Ethernet Link Aggregation; Overview; Basic Concepts - HP 6600 Configuration Manual

Configuring Ethernet link aggregation

Layer 2 aggregation groups are supported only on SAP modules operating in bridge mode.

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
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across the member ports.
Improves link reliability. The member ports dynamically back up one another. When a member port
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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 3 Ethernet link aggregation

Basic concepts

This section describes some basic link aggregation 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, 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 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
Aggregate interfaces are one of the following types:
Bridge-aggregation (BAGG) interfaces—Also called "Layer 2 aggregate interfaces."
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• Route-aggregation (RAGG) interfaces—Also called "Layer 3 aggregate interfaces." On a Layer 3
aggregate interface, you can create subinterfaces. The Layer 3 aggregate subinterfaces are logical
interfaces operating at the network layer. They can receive VLAN tagged packets for their Layer 3
aggregate interface.
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.
Figure 3, Router A and Router B are connected by three physical Ethernet links. These
"Aggregation states of member ports in an aggregation
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group."