Configuring Layer 2 Etherchannels - Cisco Catalyst 3750 Software Configuration Manual

Configuring EtherChannels
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Configuring Layer 2 EtherChannels

You configure Layer 2 EtherChannels by assigning 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 Ethernet port to a Layer 2
EtherChannel. This procedure is required.
Command
Step 1
configure terminal
Step 2 interface interface-id
Step 3 switchport mode {access | trunk}
switchport access vlan vlan-id
Catalyst 3750 Metro Switch Software Configuration Guide
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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 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 member of an EtherChannel as an 802.1x port. If 802.1x is
enabled on a not-yet active port of an EtherChannel, the port does not join the EtherChannel.
For Layer 2 EtherChannels:
– Assign all ports in the EtherChannel to the same VLAN, or configure them as trunks. Ports with
different native VLANs cannot form an EtherChannel.
– If you configure an EtherChannel from trunk ports, verify that the trunking mode (ISL or
802.1Q) is the same on all the trunks. Inconsistent trunk modes on EtherChannel ports can have
unexpected results.
– An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking
Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an
EtherChannel even when PAgP is set to the auto or desirable mode.
Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise
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compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports
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 ports in the channel.
Purpose
Enter global configuration mode.
Specify a physical port to configure, 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.
Assign all ports as static-access ports in the same VLAN, or
configure them as trunks.
If you configure the port as a static-access port, assign it to only
one VLAN. The range is 1 to 4094.
Chapter 27 Configuring EtherChannels
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