EtherChannel - prerequisites for bundling

In order for EtherChannel to successfully bundle a set of interfaces that have been configured for link aggregation, there are certain prerequisites that must be fulfilled. These are:

  1. Interface Compatibility: All interfaces in the EtherChannel bundle need to be of the same type and speed. For example, you can't bundle a Gigabit Ethernet interface with a Fast Ethernet interface.
  2. Configuration Consistency: All interfaces should have the same configuration. This includes parameters like switchport mode (access, trunk, etc.), VLAN assignments (for access mode), allowed VLANs (for trunk mode), native VLAN (for trunk mode), and Spanning Tree Protocol (STP) settings.
  3. Physical Configuration: All the interfaces should be in the same physical switch if you are configuring a Layer 2 EtherChannel. Layer 3 EtherChannels, the interfaces could be on different chassis in a high availability switch arrangement or a chassis with dual supervisors.
  4. Duplex Settings: Each of the bundled ports needs to operate in full-duplex mode.
  5. EtherChannel Protocol Compatibility: Both ends of the EtherChannel need to be running compatible aggregation protocols. Cisco supports PAgP, and LACP.
  6. Non-Disruptive Configuration: EtherChannel doesn't support any changes that could cause an outage on a single link while the bundle is live. This means no adding or removing individual links in the bundle without first disabling the entire bundle.
  7. Maximum Ports Limitation: An EtherChannel can support up to eight compatibly configured Ethernet ports. Up to 16 ports can be configured with EtherChannel, with the restriction that only the first eight will be active.