Ieee 802.3Ad Lacp Etherchannel Configuration - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 27 Configuring EtherChannel and Link State Tracking
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IEEE 802.3ad LACP EtherChannel Configuration

Cisco IOS Release 12.2(31)SGA and later releases support IEEE 802.3ad LACP EtherChannels. LACP
supports the automatic creation of EtherChannels by exchanging LACP packets between LAN ports.
LACP packets are exchanged only between ports in passive and active modes.
The protocol learns the capabilities of LAN port groups dynamically and informs the other LAN ports.
Once LACP identifies correctly matched Ethernet links, it facilitates grouping the links into an
EtherChannel. The EtherChannel is then added to the spanning tree as a single bridge port.
Both the passive and active modes allow LACP to negotiate between LAN ports to determine if they can
form an EtherChannel, based on criteria such as port speed and trunking state. Layer 2 EtherChannels
also use VLAN numbers.
LAN ports can form an EtherChannel when they are in different LACP modes as long as the modes are
compatible. For example:
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LACP uses the following parameters:
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A LAN port in desirable mode can form an EtherChannel successfully with another LAN port that
is in desirable mode.
A LAN port in desirable mode can form an EtherChannel with another LAN port in auto mode.
A LAN port in auto mode cannot form an EtherChannel with another LAN port that is also in auto
mode because neither port initiates negotiation.
A LAN port in active mode can form an EtherChannel successfully with another LAN port that is
in active mode.
A LAN port in active mode can form an EtherChannel with another LAN port in passive mode.
A LAN port in passive mode cannot form an EtherChannel with another LAN port that is also in
passive mode, because neither port initiates negotiation.
LACP system priority—You may configure an LACP system priority on each switch running LACP.
The system priority can be configured automatically or through the CLI. See the
LACP System Priority and System ID" section on page
the switch MAC address to form the system ID and also during negotiation with other systems.
The LACP system ID is the combination of the LACP system priority value and the MAC
Note
address of the switch.
LACP port priority—You must configure an LACP port priority on each port configured to use
LACP. The port priority can be configured automatically or through the CLI. See the
Layer 2 EtherChannels" section on page
form the port identifier.
LACP administrative key—LACP automatically configures an administrative key value equal to the
channel group identification number on each port configured to use LACP. The administrative key
defines the ability of a port to aggregate with other ports. A port's ability to aggregate with other
ports is determined by these factors:
Port physical characteristics, such as data rate, duplex capability, and point-to-point or shared
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Configuration restrictions that you establish
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Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
27-16. LACP uses the system priority with
27-11. LACP uses the port priority with the port number to
About EtherChannel
"Configuring the
"Configuring
27-5