Switching
Advanced EtherChannel
Advanced EtherChannel topics cover load-balancing behavior, Layer 3 EtherChannels, and consistency checks that prevent channels from forming incorrectly.
What you need to know
- Load balancing method is configured globally with port-channel load-balance and can hash on source/destination MAC, IP, or port.
- Layer 3 EtherChannels use no switchport on the port-channel and member interfaces, then an IP address on the port-channel interface.
- All member ports must have identical STP, speed, duplex, and switchport (trunk/access, native VLAN, allowed VLANs) configuration or they are suspended from the channel.
- LACP allows a maximum of 16 ports per channel-group, with only 8 active and up to 8 in hot-standby.
- The channel-group number must match on the port-channel interface configuration if manually pre-created.
- LACP port priority (lacp port-priority) determines which ports become active versus standby when more than 8 are configured.
- PAgP and LACP cannot be mixed within the same EtherChannel bundle.
Configuration commands
| Command | Mode | Purpose |
|---|---|---|
| port-channel load-balance src-dst-ip | config | Set the global load-balancing hash algorithm. |
| interface port-channel 2 | config | Create a Layer 3 port-channel interface. |
| no switchport | config-if | Convert the port-channel to a routed Layer 3 interface. |
| ip address 10.1.1.1 255.255.255.252 | config-if | Assign an IP address to the Layer 3 EtherChannel. |
| lacp port-priority 100 | config-if-range | Set LACP port priority to influence active/standby selection. |
| lacp max-bundle 4 | config-if-range | Limit the number of active links in an LACP bundle. |
| channel-protocol lacp | config-if-range | Explicitly set the negotiation protocol to LACP before assigning channel-group mode. |
Verify it
- show etherchannel summary
- show etherchannel load-balance
- show lacp neighbor
- show lacp internal
- show etherchannel 2 detail
Common mistakes
- Configuring no switchport on member ports individually instead of consistently across all members and the port-channel.
- Mismatched load-balance methods assumed to affect which ports are used rather than only traffic distribution.
- Expecting more than 8 active links in a single channel without understanding hot-standby limits.
- Mixing channel-protocol lacp and pagp commands on different members of the same group.
- Not checking show etherchannel summary flags (e.g. suspended 's' state) when a member fails to join.
Practise Advanced EtherChannel in a real CLI
Generated labs, graded against the simulated network state.