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Configuring ethernet link aggregation, Basic concepts – H3C Technologies H3C S5560 Series Switches User Manual

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Configuring Ethernet link aggregation

Ethernet link aggregation bundles multiple physical Ethernet links into one logical link, called an

aggregate link. Link aggregation has the following benefits:

Increased bandwidth beyond the limits of any single link. In an aggregate link, traffic is distributed
across the member ports.

Improved 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

Figure 8

, Device A and Device B are connected by three physical Ethernet links. These

physical Ethernet links are combined into an aggregate link called link aggregation 1. The bandwidth of

this aggregate link can reach up to the total bandwidth of the three physical Ethernet links. At the same

time, the three Ethernet links back up one another. When a physical Ethernet link fails, the traffic
previously carried on the failed link is switched to the other two links.

Figure 8 Ethernet link aggregation diagram

Basic concepts

Aggregation group, member port, and aggregate interface

Link bundling is implemented through interface bundling. An aggregation group is a group of Ethernet

interfaces bundled together, which are called member ports of the aggregation group. For each

aggregation group, a logical interface (called an aggregate interface), is created. When an upper layer
entity uses the link aggregation service, the following events occur:

A link aggregation group appears the same as a single logical link.

An aggregate interface transmits data traffic.

When you create an aggregate interface, the device automatically creates an aggregation group of the

same type and number as the aggregate interface. For example, when you create aggregate interface

1, aggregation group 1 is created.
Aggregate interfaces include Layer 2 aggregate interfaces and Layer 3 aggregate interfaces.
You can assign Layer 2 Ethernet interfaces only to a Layer 2 aggregation group, and Layer 3 Ethernet

interfaces only to a Layer 3 aggregation group.

NOTE:

You can use the port link-mode command to configure an Ethernet port as a Layer 2 or Layer 3 interface
(see "Configuring Ethernet interfaces").