23Ethernet link aggregation configurationThis chapter includes these sections:• Overview• Ethernet link aggregation configuration task list• Displaying and maintaining Ethernet link aggregation• Ethernet link aggregation configuration examplesOverviewEthernet link aggregation, or simply link aggregation, combines multiple physical Ethernet ports into onelogical 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 distributedacross the member ports.• Improves link reliability. The member ports dynamically back up one another. When a member portfails, its traffic is automatically switched to other member ports.As shown in Figure 5, Device A and Device B are connected by three physical Ethernet links. Thesephysical Ethernet links are combined into an aggregate link, Link aggregation 1. The bandwidth of thisaggregate link is as high as the total bandwidth of these three physical Ethernet links. At the same time,the three Ethernet links back up each other.Figure 5 Diagram for Ethernet link aggregationBasic conceptsAggregation group, member port, aggregate interfaceLink aggregation is implemented through link aggregation groups. An aggregation group is a group ofEthernet interfaces aggregated together, which are called member ports of the aggregation group. Foreach aggregation group, a logical interface, called an aggregate interface, is created. To an upperlayer entity that uses the link aggregation service, a link aggregation group looks like a single logical linkand data traffic is transmitted through the aggregate interface.When you create an aggregate interface, the switch automatically creates an aggregation group of thesame type and number as the aggregate interface. For example, when you create interfaceBridge-aggregation 1, Layer 2 aggregation group 1 is created.You can assign Layer 2 Ethernet interfaces only to a Layer 2 aggregation group.
