Etherchannel Configuration Overview - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 27 Configuring EtherChannel and Link State Tracking
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EtherChannel Configuration Overview

You can configure EtherChannels manually or use the Port Aggregation Control Protocol (PAgP) or the
Link Aggregation Control Protocol (LACP) (Cisco IOS Release 12.2(31)SGA and later), to form
EtherChannels. The EtherChannel protocols allow ports with similar characteristics to form an
EtherChannel through dynamic negotiation with connected network devices. PAgP is a
Cisco-proprietary protocol and LACP is defined in IEEE 802.3ad.
PAgP and LACP do not interoperate. Ports configured to use PAgP cannot form EtherChannels with
ports configured to use LACP and vice versa.
Table 27-1
Table 27-1
Mode
on
auto
desirable
passive
active
Manual EtherChannel Configuration
Manually configured EtherChannel ports do not exchange EtherChannel protocol packets. A manually
configured EtherChannel forms only when you configure all ports compatibly in the EtherChannel.
Auto-LAG
You can automatically create EtherChannels on ports connected to a switch, using auto-LAG. By default,
auto-LAG is disabled globally, but is enabled on all port interfaces. To configure auto-LAG on your
switch, ensure that you enable auto-LAG globally.
When auto-LAG is enabled globally:
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PAgP EtherChannel Configuration, page 27-4
IEEE 802.3ad LACP EtherChannel Configuration, page 27-5
lists the user-configurable EtherChannel modes.
EtherChannel Modes
Description
Mode that forces the LAN port to channel unconditionally. In the on mode, a usable
EtherChannel exists only when a LAN port group in the on mode is connected to another
LAN port group in the on mode. Because ports configured in the on mode do not negotiate,
there is no negotiation traffic between the ports.
PAgP mode that places a LAN port into a passive negotiating state in which the port
responds to PAgP packets it receives but does not initiate PAgP negotiation.
PAgP mode that places a LAN port into an active negotiating state in which the port
initiates negotiations with other LAN ports by sending PAgP packets.
LACP mode that places a port into a passive negotiating state in which the port responds
to LACP packets it receives but does not initiate LACP negotiation.
LACP mode that places a port into an active negotiating state in which the port initiates
negotiations with other ports by sending LACP packets.
All port interfaces participate in the creation of auto EtherChannels if the partner port interfaces
have EtherChannel configured on them. For more information, see
configuration on actor and partner devices, page
Ports that are already part of manual EtherChannels cannot participate in creation of auto
EtherChannels.
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Table 27-1Supported auto-LAG
27-4.
About EtherChannel
27-3