Understanding LACP on Stand-Alone Devices

Link Aggregation Control Protocol (LACP) provides a standardized means for exchanging information between partner systems on a link. Within LACP, the local end of a child link is known as the actor and the remote end of the link is known as the partner.

LACP is enabled on an aggregated Ethernet interface by setting the mode to either passive or active. However, to initiate the transmission of link aggregation control protocol data units (PDUs) and response link aggregation control PDUs, you must enable LACP at both the local and remote ends of the links, and one end must be active:

• Active mode—If either the actor or partner is active, they exchange link aggregation control PDUs. The actor sends link aggregation control PDUs to its protocol partner that convey what the actor knows about its own state and that of the partner’s state.
• Passive mode—If the actor and partner are both in passive mode, they do not exchange link aggregation control PDUs. As a result, the aggregated Ethernet links do not come up. In passive transmission mode, links send out link aggregation control PDUs only when they receive them from the remote end of the same link.

By default, the actor and partner transmit link aggregation control PDUs every second. You can configure different periodic rates on active and passive interfaces. When you configure the active and passive interfaces at different rates, the transmitter honors the receiver’s rate.

You configure the interval at which the interfaces on the remote side of the link transmit link aggregation control PDUs by configuring the periodic statement on the interfaces on the local side. It is the configuration on the local side that specifies the behavior of the remote side. That is, the remote side transmits link aggregation control PDUs at the specified interval. The interval can be fast (every second) or slow (every 30 seconds).