Link Aggregation Control Protocol - Lenovo Flex System Fabric CN4093 Application Manual

Link Aggregation Control Protocol

© Copyright Lenovo 2015
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.
IEEE 802.3ad 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 or
links of the dynamic trunk group.
The CN4093 supports up to 64 LACP trunks, each with up to 16 ports.
Note: LACP implementation in Lenovo N/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: 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 CN4093 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 CN4093) and a Partner (another
switch), as shown in Table
Table 17.
Actor vs. Partner LACP configuration
Actor Switch
Port 38 (admin key = 100)
Port 39 (admin key = 100)
Port 40 (admin key = 100)
In the configuration shown in Table
form an LACP trunk group with Partner switch ports 1 and 2. Only ports with the
same LAG ID are aggregated in the trunk group. Actor switch port 40 is not
aggregated in the trunk group because it has a different LAG ID. Switch ports
configured with the same admin key on the Actor switch but have a different LAG
ID (due to Partner switch admin key configuration or due to partner switch MAC
address being different) can be aggregated in another trunk group. i.e. Actor
switch port 40 can be aggregated in another trunk group with ports that have the
same LAG ID as port 40.
17.
Partner Switch 1
Port 1 (admin key = 50)
Port 2 (admin key = 50)
Port 3 (admin key = 70)
17, Actor switch ports 38 and 39 aggregate to
Chapter 10: Ports and Trunking
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