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Catalyst 2960 Switch SoftwareConfiguration Guide
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Chapter30 Configuring EtherChannels
Configuring EtherChannels
•Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running
PAgP and LACP can coexist on the same switch. Individual EtherChannel groups can run either
PAgP or LACP, but they cannot interoperate.
•Do not configure a Switched Port Analyzer (SPAN) destination port as part of an EtherChannel.
•Do not configure a secure port as part of an EtherChannel or the reverse.
•Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an
IEEE 802.1x port. If you try to enable IEEE 802.1x on a n EtherChannel port, an error message
appears, and IEEE 802.1x is not enabled.
•If EtherChannels are configured on switch interfaces, remove the EtherChannel con figuration from
the interfaces before globally enabling IEEE 802.1x on a sw itch by using the dot1x
system-auth-control global configuration command.
•For Layer 2 EtherChannels:
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Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with
different native VLANs cannot form an EtherChannel.
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If you configure an EtherChannel from trunk ports, verify that the trunking mode (ISL or
IEEE 802.1Q) is the same on all the trunks. In consistent trunk modes on EtherChannel ports can
have unexpected results.
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An EtherChannel supports the same allowed range of VLANs on all the po rts in a trunking
Layer 2 EtherChannel. If the allowed range of VLANs is not th e same, the ports do not form an
EtherChannel even when PAgP is set to the auto or desirable mode.
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Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise
compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports
incompatible for the formation of an EtherChannel.
Configuring Layer 2 EtherChannels
You configure Layer2 EtherChannels by assig ning ports to a channel group with the channel-group
interface configuration command. This command automatically creates the port-channel logical
interface.
Beginning in privileged EXEC mode, follow these steps to assign a Layer 2 E thernet port to a Layer 2
EtherChannel. This procedure is required.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify a physical port, and enter interface configuration mode.
Valid interfaces include physical ports.
For a PAgP EtherChannel, you can configure up to eight ports of
the same type and speed for the same group.
For a LACP EtherChannel, you can configure up to 16 Ethernet
ports of the same type. Up to eight ports can be active, and up to
eight ports can be in standby mode.