Reference Guide

Link Aggregation Control Protocol (LACP) | 537
28
Link Aggregation Control Protocol (LACP)
Link Aggregation Control Protocol (LACP) is supported on the S5000 switch.
The major sections in the chapter are:
• Introduction to Dynamic LAGs and LACP
• LACP Configuration Tasks
• Shared LAG State Tracking
Introduction to Dynamic LAGs and LACP
A Link Aggregation Group (LAG), referred to as a port channel by Dell Networking OS, can provide both
load-sharing and port redundancy across stack units. LAGs can be enabled as static or dynamic. The
benefits and constraints are basically the same, as described in Port Channel Interfaces in the Interfaces
chapter.
The unique benefit of a dynamic LAG is that its ports can toggle between participating in the LAG or
acting as dedicated ports, whereas ports in a static LAG must be specifically removed from the LAG in
order to act alone.
Dell Networking OS uses LACP to create dynamic LAGs. LACP provides a standardized means of
exchanging information between two systems (also called Partner Systems) and automatically establishes
the LAG between the systems. LACP permits the exchange of messages on a link to allow their LACP
instances to:
• Reach agreement on the identity of the LAG to which the link belongs.
• Move the link to that LAG.
• Enable the transmission and reception functions in an orderly manner.
The Dell Networking OS implementation of LACP is based on the standards specified in the IEEE 802.3:
“Carrier sense multiple access with collision detection (CSMA/CD) access method and physical layer
specifications.”
LACP functions by constantly exchanging custom MAC PDUs across LAN Ethernet links. The protocol
packets are only exchanged between ports that are configured as LACP capable.