13-2
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 13 Configuring EtherChannels
Understanding How EtherChannels Work
EtherChannel Feature Overview
An EtherChannel bundles individual Ethernet links into a single logical link that provides the aggregate
bandwidth of up to eight physical links.
A Catalyst 6500 series switch supports a maximum of 64 EtherChannels (256 with Release 12.1(2)E and
earlier). You can form an EtherChannel with up to eight compatibly configured LAN ports on any
module in a Catalyst 6500 series switch. All LAN ports in each EtherChannel must be the same speed
and must all be configured as either Layer 2 or Layer 3 LAN ports.
Note The network device to which a Catalyst 6500 series switch is connected may impose its own limits on
the number of ports in an EtherChannel.
If a segment within an EtherChannel fails, traffic previously carried over the failed link switches to the
remaining segments within the EtherChannel. When a failure occurs, the EtherChannel feature sends a
trap that identifies the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast
packets on one segment in an EtherChannel are blocked from returning on any other segment of the
EtherChannel.
Understanding How EtherChannels Are Configured
These sections describe how EtherChannels are configured:
• EtherChannel Configuration Overview, page 13-2
• Understanding Manual EtherChannel Configuration, page 13-3
• Understanding PAgP EtherChannel Configuration, page 13-3
• Understanding IEEE 802.3ad LACP EtherChannel Configuration, page 13-3

EtherChannel Configuration Overview

You can configure EtherChannels manually or you can use the Port Aggregation Control Protocol
(PAgP) or, with Release 12.1(13)E and later, the Link Aggregation Control Protocol (LACP) 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 with each other. Ports configured to use PAgP cannot form
EtherChannels with ports configured to use LACP. Ports configured to use LACP cannot form
EtherChannels with ports configured to use PAgP.
Table 13-1 lists the user-configurable EtherChannel modes.