46LACPLACP uses LACPDUs to exchange aggregation information between LACP-enabled devices.Each member port in an LACP-enabled aggregation group exchanges information with its peer. When amember port receives an LACPDU, it compares the received information with information received on theother member ports. In this way, the two systems reach an agreement on which ports are placed inSelected state.LACP functionsLACP offers basic LACP functions and extended LACP functions, as described in Table 3.Table 3 Basic and extended LACP functionsCategory DescriptionBasic LACP functions Implemented through the basic LACPDU fields, including the system LACP priority,system MAC address, port priority, port number, and operational key.Extended LACPfunctionsImplemented by extending the LACPDU with new TLV fields. This is how the LACPMAD mechanism of the IRF feature is implemented.The switch series can participate in LACP MAD as either an IRF member device or anintermediate device.For more information about IRF and the LACP MAD mechanism, see IRFConfiguration Guide.LACP operating modesLACP can operate in active mode or passive mode.When LACP is operating in passive mode on a local member port and its peer port, both ports cannotsend LACPDUs. When LACP is operating in active mode on the port on either end of a link, both portscan send LACPDUs.LACP prioritiesLACP priorities include system LACP priority and port priority, as described in Table 4. The smaller thepriority value, the higher the priority.Table 4 LACP prioritiesType DescriptionSystem LACP priorityUsed by two peer devices (or systems) to determine which one is superior in linkaggregation.In dynamic link aggregation, the system that has higher system LACP priority sets theSelected state of member ports on its side, after which the system that has lower prioritysets port state accordingly.Port priority Determines the likelihood of a member port to be a Selected port on a system. Thehigher port priority, the higher the likelihood of selection.LACP timeout intervalThe LACP timeout interval specifies how long a member port waits to receive LACPDUs from the peer port.If a local member port has not received LACPDUs from the peer within the LACP timeout interval, themember port considers the peer as failed.
