Link Aggregation Control Protocol

Link Aggregation Control Protocol (LACP) is an IEEE standards-based protocol that allows two partner systems to dynamically negotiate attributes of physical links between them to form logical links.

LACP enables devices to send Link Aggregation Control Protocol Data Units (LACPDUs) to each other and establish link aggregation connections.

The NPB application supports the following LACP functionality:

Adding or removing LAG or port channel.
Performing required validations before adding member ports into a LAG.
Publishing LAG interface status and LAG-IfIndex to State DB.
Managing LAG member ports.

LACP Modes

LACP operates in two modes:

Active mode: LACP initiates protocol data unit (PDU) exchanges, regardless of whether the partner system sends LACP PDUs.
Passive mode: LACP responds to PDUs initiated by its partner system, but does not initiate the LACP PDU exchange.

LACP System Priority

LACP combines the system priority with the MAC address of the switch to form the system ID, and also during negotiation with other switches. The system priority value range is 1 through 65535. The lower numbered system priority values have higher priorities. The default system priority value is 32768.

LACP Timers

LACP timer attributes allow customization of failover time:

Fast periodic time: LACPDU exchange time is 1 sec and timeout is 3 sec (3 x 1).
Slow or normal periodic time: LACPDU exchange time is 30 sec and timeout is 90 sec (3 x 30).

The values are set to match the IEEE 802.3ad values by default. The default LACP timer is slow or normal periodic time.

LACP Port Priority

Each port configured to use LACP has an LACP port priority. LACP port priorities range from 1 to 65535. The lower numbered port priority values have higher priorities. LACP combines the port priority and port number to create the port identifier. The port priority is used to determine standby mode ports when there is a hardware limitation that prevents all compatible ports from aggregating. The default port priority value is 32786.