Cisco Catalyst 3550 Series User Manual

30-9
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 30 Configuring EtherChannels
Configuring EtherChannels
• Before enabling 802.1X on the port, you must first remove it from the EtherChannel. If you try to
enable 802.1X on an EtherChannel or on an active port in an EtherChannel, an error message
appears, and 802.1X is not enabled. If you enable 802.1X on a not-yet active port of an
EtherChannel, the port does not join the EtherChannel.
• For Layer 2 EtherChannels:
– Assign all interfaces in the EtherChannel to the same VLAN, or configure them as trunks.
Interfaces with different native VLANs cannot form an EtherChannel.
– If you configure an EtherChannel from trunk interfaces, verify that the trunking mode (ISL or
802.1Q) is the same on all the trunks. Inconsistent trunk modes on EtherChannel interfaces can
have unexpected results.
– An EtherChannel supports the same allowed range of VLANs on all the interfaces in a trunking
Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the interfaces do not
form an EtherChannel even when PAgP is set to the auto or desirable mode.
– Interfaces 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 interfaces incompatible for the formation of an EtherChannel.
• For Layer 3 EtherChannels, assign the Layer 3 address to the port-channel logical interface, not to
the physical interfaces in the channel.
Configuring Layer 2 EtherChannels
You configure Layer 2 EtherChannels by configuring the Ethernet interfaces with the channel-group
interface configuration command, which creates the port-channel logical interface. You cannot put a
Layer 2 interface into a manually created port-channel interface.
Note Layer 2 interfaces must be connected and functioning for Cisco the software to create port-channel
interfaces.
Beginning in privileged EXEC mode, follow these steps to assign a Layer 2 Ethernet interface to a
Layer 2 EtherChannel:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify a physical
interface to configure.
Valid interfaces include physical interfaces.
Up to eight interfaces of the same type and speed can be
configured for the same group.
Step 3
switchport mode {access | trunk}
switchport access vlan vlan-id
Assign all interfaces as static-access ports in the same VLAN, or
configure them as trunks.
If you configure the interface as a static-access port, assign it to
only one VLAN. The range is 1 to 4094.

Cisco Catalyst 3550 Series Specifications

General

Brand	Cisco
Model	Catalyst 3550 Series
Category	Network Router
Language	English