Configuring Etherchannels - Cisco Catalyst 4500 series Administration Manual

Chapter 26 Configuring EtherChannel and Link State Tracking
After you configure an EtherChannel, the configuration that you apply to the port channel interface
affects the EtherChannel; the configuration that you apply to the physical interfaces affects only the
interface where you apply the configuration. To change the parameters of all ports in an EtherChannel,
apply configuration commands to the port channel interface (such commands can be STP commands or
commands to configure a Layer 2 EtherChannel as a trunk).

Configuring EtherChannels

These subsections describe how EtherChannels are configured:
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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(25)EWA 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 26-1
Table 26-1
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.
OL_28731-01
EtherChannel Configuration Overview, page 26-3
Manual EtherChannel Configuration, page 26-3
PAgP EtherChannel Configuration, page 26-4
IEEE 802.3ad LACP EtherChannel Configuration, page 26-4
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.
Software Configuration Guide—Release IOS XE 3.6.0E and IOS 15.2(2)E
About EtherChannel
26-3