Users Guide

Table Of Contents
Dell PowerConnect ArubaOS 5.0 | User Guide] Link Aggregation Control Protocol | 489
Chapter 25
Link Aggregation Control Protocol
Dell PowerConnect implementation of Link Aggregation Control Protocol (LACP) is based on the standards
specified in 802.3ad. LACP provides a standardized means for exchanging information, with partner systems, to
form a link aggregation group (LAG). LACP avoids port channel misconfiguration.
Two devices (actor and partner) exchange LACP data units (DUs) in the process of forming a LAG. Once
multiple ports in the system have the same actor system ID, actor key, partner system ID, and partner key, they
belong to the same LAG.
The maximum number of supported port-channels is 8. With the introduction of LACP, this number remains
the same. In essence, a port-channel group (LAG) is created either statically or dynamically via LACP. This
chapter contains:
z “Important Points to Remember” on page489
z “Configuring LACP” on page489
z “Best Practices” on page491
z “Sample Configuration” on page492
Important Points to Remember
z LACP is disabled by default
z LACP depends on periodical Tx/Rx of LACP data units (LACPDU). Any failures are noticed immediately and
that port is removed from the LAG
z The maximum LAG supported per system is 8 groups; each group can be created statically or via LACP
z Each LAG can have up to 8 member ports
z The LAG group identification (ID) range is 0 to 7 for both static (port-channel) and LACP groups
z When a port is added to a LACP LAG, it inherits the port-channel’s properties (i.e. VLAN membership, trunk
status etc)
z When a port is added to LACP LAG, the port’s property (i.e. speed) is compared to the existing port
properties. If there is a mismatch, the command is rejected.
Configuring LACP
Two LACP configured devices exchange LACPDUs to form a LAG. A device is configurable as an active or
passive participant. In active mode, the device initiates DUs irrespective of the partner state; passive mode
devices respond only to the incoming DUs sent by the partner device. Hence, to form a LAG group between two
devices, one device must be an active participant. For detailed information on the LACP commands, see the
ArubaOS Command Line Reference Guide.
In the CLI
LACPDUs exchange their corresponding system identifier/priority along with their port’s key/priority. This
information determines the LAG of a given port. The LAG for a port is selected based on it’s keys; the port is
placed in that LAG only when it’s system ID/key and partner's system ID/key matches the other ports in the LAG
(if the group has ports).