JUNOS Enterprise Switching

Aggregated Ethernet

Aggregated Ethernet (AE) enables you to group multiple Ethernet interfaces to form a single physical link at the MAC layer, allowing you to increase your speed beyond what a single link can provide, as well as increasing redundancy. AE has had several names over the years. Officially, it is a standard in 802.1AX; however, many people still refer to it as 802.3ad because it appeared in section 41 of that standard. Other names that have been used by various vendors include NIC teaming, port channel, port teaming, port trunking, link bundling, and EtherChannel. In this chapter, however, we will refer to the link as AE.

Note

How does a standard get its name, such as 802.1AX or 802.3ad? Well, the 802 refers to an actual working group for the standard. The letters themselves have no meaning; letters are just incremented starting from a and going to z. So, in order: a, aa, ab, b, bb, and so on. The capitalization indicates a standalone document, whereas lowercase denotes a supplement to an existing document. At least, that was the idea when the naming convention was created.

Historically, link aggregation is configured statically, meaning that the local device bonds the physical interfaces together. This meant that there was no way to link path failures (if there was an intermediate device) or to know whether the other end of the link was also bundling the interface. For that reason, the industry-standard Link Aggregation Control Protocol (LACP) was created. Essentially, ...