Administrator Guide

Link Aggregation Control Protocol (LACP)
A link aggregation group (LAG), referred to as a port channel by the Dell EMC 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 LACP
A link aggregation group (LAG), referred to as a port channel by Dell EMC Networking OS, can provide both load-sharing and port
redundancy across line cards. You can enable LAGs as static or dynamic.
The benets and constraints are basically the same, as described in Port Channel Interfaces in the Interfaces chapter.
The unique benet 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.
The Dell EMC 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 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 EMC Networking OS implementation of LACP is based on the standards specied in the IEEE 802.3: “Carrier sense multiple
access with collision detection (CSMA/CD) access method and physical layer specications.”
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 congured 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 dened 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.
– If a physical interface is a part of a dynamic LAG, it cannot be added as a member of a static LAG. The channel-member
tengigabitethernet command is rejected in the static LAG interface for that physical interface.
• A dynamic LAG can be created with any type of conguration.
• There is a dierence between the shutdown and no interface port-channel commands:
– The shutdown command on LAG “xyz” disables the LAG and retains the user commands. However, the system does not allow the
channel number “xyz” to be statically created.
– The no interface port-channel channel-number command deletes the specied LAG, including a dynamically created
LAG. This command removes all LACP-specic commands on the member interfaces. The interfaces are restored to a state that is
ready to be congured.
NOTE
: There is no conguration on the interface because that condition is required for an interface to be part of a
LAG.
• You can congure link dampening on individual members of a LAG.
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