Configuring EtherChannel Between Catalyst Switches Running Cisco IOS System Software and a Cisco Router
Document ID: 21066
Introduction Prerequisites Requirements Components Used Conventions Important Notes Configure Network Diagram Configurations Verify show Commands Sample show Command Output Troubleshoot NetPro Discussion Forums − Featured Conversations Related Information

Introduction
This sample configuration demonstrates how to set up a Layer 3 (L3) EtherChannel, without VLAN trunking, between a Cisco router and a Cisco Catalyst 6500 switch running Cisco IOS® System Software. EtherChannel can be called Fast EtherChannel (FEC) or Gigabit EtherChannel (GEC); the term depends on the speed of the interfaces or ports you use to form …ver más…

You must configure the port−channel interface before you configure the channel group under the physical interface. The order of configuration of a port channel in Catalyst 6500/6000 and 4500/4000 Cisco IOS Software is important. It is best to issue any switchport command before you issue the channel−group command in a physical interface. When you issue the channel−group command prior to the switchport command on a physical interface (interface Gigabit Ethernet 1/1), the port−channel interface is created automatically and becomes a L3 interface. If you then issue the switchport command under the physical interface, the physical interface becomes a L2 interface. Also, the port−channel interface that you created earlier has no physical interface

associated with it. Notice that the channel−group command is absent from under the physical interface. In this case, you must first issue the switchport command under the newly configured port−channel interface. Then, the physical port accepts the channel−group command again. In this case, the port channel has changed from a L3 interface to a L2 interface. Consider, in contrast, if you issue the switchport command first on a physical interface and then add the channel−group command. In this case, the port−channel interface is automatically created and inherits all the configured switchport commands. On a Catalyst 6500/6000 switch running Cisco IOS Software, all ports are L3 ports by default. On a Catalyst