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BLADEOS 6.5.2 Application Guide
BMD00220, October 2010 Chapter 7: Ports and Trunking 107
Link Aggregation Control Protocol
Link Aggregation Control Protocol (LACP) is an IEEE 802.3ad standard for grouping several
physical ports into one logical port (known as a dynamic trunk group or Link Aggregation group)
with any device that supports the standard. Please refer to IEEE 802.3ad-2002 for a full description
of the standard.
The 802.3ad standard allows standard Ethernet links to form a single Layer 2 link using the Link
Aggregation Control Protocol (LACP). Link aggregation is a method of grouping physical link
segments of the same media type and speed in full duplex, and treating them as if they were part of
a single, logical link segment. If a link in a LACP trunk group fails, traffic is reassigned
dynamically to the remaining link(s) of the dynamic trunk group.
Note – LACP implementation in the BLADEOS does not support the Churn machine, an option
used to detect if the port is operable within a bounded time period between the actor and the partner.
Only the Marker Responder is implemented, and there is no marker protocol generator.
A port’s Link Aggregation Identifier (LAG ID) determines how the port can be aggregated. The
Link Aggregation ID (LAG ID) is constructed mainly from the system ID and the port’s admin key,
as follows:
System ID: an integer value based on the switch’s MAC address and the system priority
assigned in the CLI.
Admin key: a port’s Admin key is an integer value (1-65535) that you can configure in the
CLI. Each switch port that participates in the same LACP trunk group must have the same
admin key value. The Admin key is local significant, which means the partner switch does not
need to use the same Admin key value.
For example, consider two switches, an Actor (the G8124) and a Partner (another switch), as shown
in Table 10.
In the configuration shown in Table 10, Actor switch port 7 and port 8 aggregate to form an LACP
trunk group with Partner switch port 1 and port 2.
LACP automatically determines which member links can be aggregated and then aggregates them.
It provides for the controlled addition and removal of physical links for the link aggregation.
Table 10 Actor vs. Partner LACP configuration
Actor Switch Partner Switch 1
Port 7 (admin key = 100) Port 1 (admin key = 50)
Port 8 (admin key = 100) Port 2 (admin key = 50)