Configuring EtherChannel
Guidelines and best practices for configuring EtherChannel

Follow these guidelines and restrictions when configuring EtherChannel interfaces:

  • EtherChannel Support – All Ethernet interfaces on all modules support EtherChannel (maximum of eight interfaces), with no requirement that interfaces be physically contiguous or on the same module.
  • Speed and Duplex – Configure all interfaces in an EtherChannel to operate at the same speed and in the same duplex mode. Also, if one interface in the bundle is shut down it is treated as a link failure and traffic will traverse other links in the bundle.
  • SPAN and Etherchannel – An EtherChannel will not form if one of the interfaces is a Switched Port Analyzer (SPAN) destination port.
  • For Layer 3 EtherChannels – Assign Layer 3 addresses to the port-channel logical interface, not to the physical interfaces in the channel.
  • VLAN match – All interfaces in the EtherChannel bundle must be assigned to the same VLAN or be configured as a trunk
  • Range of VLANs – 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 set to the auto or desirable mode. For Layer 2 EtherChannels, either assign all interfaces in the EtherChannel to the same VLAN or configure them as trunks.
  • STP Path Cost – Interfaces with different STP port path costs can form an EtherChannel as long they are otherwise compatibly configured. Setting different STP port path costs does not, by itself, make interfaces incompatible for the formation of an EtherChannel.
  • Port Channel vs. Interface configuration – After configuring an EtherChannel, any configuration you apply to the port-channel interface affects the EtherChannel. Any configuration you apply to the physical interfaces affects only the specific interface you configured.