Link aggregation is the ability to create one logical link using multiple physical links between two devices. This allows load sharing among the physical links, rather than having STP block one or more of the links. EtherChannel is a form of link aggregation used in switched networks.

This chapter describes EtherChannel and the methods used to create an EtherChannel. An EtherChannel can be manually configured or can be negotiated by using the Cisco-proprietary protocol Port Aggregation Protocol (PAgP) or the IEEE 802.3ad-defined protocol Link Aggregation Control Protocol (LACP). The configuration, verification, and troubleshooting of EtherChannel are discussed.