Link Aggregation Control Protocol (Lacp); Introduction To Dynamic Lags And Lacp; Important Points To Remember - Dell C9000 Series Networking Configuration Manual

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Link Aggregation Control Protocol

A link aggregation group (LAG), referred to as a port channel by the Dell Networking OS, can provide both

load-sharing and port redundancy across line cards. You can enable LAGs as static or dynamic.

Introduction to Dynamic LAGs and

The 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.

The benefits and constraints of a LAG are basically the same as a port channel, as described in Port Channel

Interfaces in the

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 removed from the

LAG in order to act alone.

LACP permits the exchange of messages on a link to allow their LACP instances to:

Reach an 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 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 units (PDUs) across local area network

(LAN) Ethernet links. The protocol packets are only exchanged between ports that are configured as LACP

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 (the 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 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.

Link Aggregation Control Protocol (LACP)