RackSwitch G8000 Application Guide
70
Chapter 4: Ports and Trunking BMD00041, November 2008
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 physi-
cal 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 reas-
signed dynamically to the remaining link(s) of the dynamic trunk group.
NOTE – LACP implementation in the Blade OS 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 is 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 (53-65535) 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 G8000) and a Partner (another switch), as
shown in Table 4-1.
In the configuration shown in Table 4-1, Actor switch port 7 and port 8 aggregate to form an
LACP trunk group with Partner switch port 1 and port 2.
Table 4-1 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)
