LACP Operation

In order to allow LACP to determine whether a set of links connect to the same device, and to determine whether those links are compatible from the point of view of aggregation, it is necessary to be able to establish:

• A globally unique identifier for each device that participates in link aggregation.
• A means of identifying the set of capabilities associated with each port and with each aggregator, as understood by a given device.
• A means of identifying a LAG and its associated aggregator.

For each aggregatable port in the device, LACP:

• Maintains configuration information (reflecting the inherent properties of the individual links as well as those established by network administration) to control aggregation.
• Exchanges configuration information with other devices to allocate the link to a LAG.
  

  Note

  A given link is allocated to, at most, one LAG at a time. The allocation mechanism attempts to maximize aggregation, subject to management controls.
• Attaches the port to the aggregator used by the LAG, and detaches the port from the aggregator when it is no longer used by the LAG.
• Uses information from the partner device‘s link aggregation control entity to decide whether to aggregate ports.

The operation of LACP involves the following activities:

• Checking that candidate links can actually be aggregated.
• Controlling the addition of a link to a LAG and the creation of the group if necessary.
• Monitoring the status of aggregated links to ensure that the aggregation is still valid.
• Removing a link from a LAG if its membership is no longer valid, and removing the group if it no longer has any member links.