24Link Aggregation Control Protocol (LACP)A link aggregation group (LAG), referred to as a port channel by the Dell Networking OS, can provide bothload-sharing and port redundancy across line cards. You can enable LAGs as static or dynamic.Introduction to Dynamic LAGs and LACPA link aggregation group (LAG), referred to as a port channel by Dell Networking OS, can provide bothload-sharing and port redundancy across line cards. You can enable LAGs as static or dynamic.The benefits and constraints are basically the same, as described in Port Channel Interfaces in theInterfaces chapter.The unique benefit of a dynamic LAG is that its ports can toggle between participating in the LAG oracting as dedicated ports, whereas ports in a static LAG must be removed from the LAG in order to actalone.The Dell Networking OS uses LACP to create dynamic LAGs. LACP provides a standardized means ofexchanging information between two systems (also called Partner Systems) and automatically establishesthe LAG between the systems. LACP permits the exchange of messages on a link to allow their LACPinstances 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 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 layerspecifications.”LACP functions by constantly exchanging custom MAC protocol data units (PDUs) across local areanetwork (LAN) Ethernet links. The protocol packets are only exchanged between ports that areconfigured 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 (the channel-membercommand), 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 isrejected 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 x/y command is rejected in the static LAGinterface for that physical interface.496 Link Aggregation Control Protocol (LACP)
