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31-9
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
78-11380-10
Chapter 31 Configuring EtherChannels
Configuring EtherChannels
• An EtherChannel supports the same allowed range of VLANs on all the interfaces in a trunking
Layer 2 EtherChannel. When configuring an interface for PAgP, 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. When configuring an interface for LACP, if the allowed range of VLANs is not the
same, the interfaces do not form an EtherChannel even when LACP is set to the active or passive
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.
• Configure only PAgP-type EtherChannels on Catalyst 2950 Long-Reach Ethernet (LRE) switch
ports.
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 Specify a physical interface to configure, and enter interface
configuration mode.
Valid interfaces include physical interfaces.
Up to eight interfaces of the same type and speed can be
configured for the same group.