Introduction to Link Aggregation

Definition

Ethernet link aggregation, also called Eth-Trunk, bundles multiple physical links to form a logical link to increase link bandwidth. The bundled links implement redundancy, increasing reliability.

Purpose

As the network scale expands, users have increasingly high requirements on the bandwidth and reliability of the Ethernet backbone network. Originally, to increase the bandwidth, users used high-speed cards or devices with high-speed interface cards to replace old interface cards or devices. This solution, however, is costly and inflexible.

Link aggregation increases bandwidth by bundling a group of physical interfaces into a single logical interface, without the need to upgrade hardware. In addition, link aggregation provides link backup mechanisms, greatly improving link reliability.

Link aggregation has the following advantages:

• Increased bandwidth

  The bandwidth of the link aggregation interface is the sum of bandwidth of member interfaces.

• Higher reliability

  When an active link fails, traffic on this active link is switched to another active link, improving reliability of the link aggregation interface.

• Load balancing

  In a link aggregation group (LAG), traffic is load balanced among active links of member interfaces.