Ethernet link aggregation bundles multiple physical Ethernet links into one logical link, called a link aggregation group (LAG).

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 the following figure 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 originally intended for the failed link is switched to the remaining active links.

    Ethernet link aggregation diagram