Reference Guide

Link Aggregation Control Protocol (LACP) | 523
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Link Aggregation Control Protocol (LACP)
Link Aggregation control protocol (LACP) is supported on the MXL Switch platform.
Introduction to Dynamic LAGs and LACP
A link aggregation group (LAG), referred to as a port channel by the Dell Networking operating software
(FTOS), provides both load-sharing and port redundancy across stack units. You can enable LAGs as static
or dynamic. The benefits and constraints are basically the same, as described in Port Channel Interfaces in
Interfaces.
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.
FTOS 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 FTOS 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 protocol data unit (PDUs) across LAN Ethernet
links. The protocol packets are only exchanged between ports that are configured as LACP capable.
Important Points to Remember
• LACP allows you to add members to a port channel (LAG) as long as it has no static members.
Conversely, if the LAG already contains a statically defined member (
channel-member command), the
port-channel mode command is not permitted.
• A static LAG cannot be created if a dynamic LAG using the selected number already exists.
• No dual membership in static and dynamic LAGs:
• If a physical interface is a part of a static LAG, the
port-channel-protocol lacp command is rejected on
that interface.