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! Step 1: Configure the member interfacesSW1(config)# interface range gigabitEthernet0/1 - 4SW1(config-if-range)# description EtherChannel-to-SW2SW1(config-if-range)# switchportSW1(config-if-range)# switchport mode trunkSW1(config-if-range)# switchport trunk allowed vlan 10,20,30SW1(config-if-range)# channel-group 1 mode activeSW1(config-if-range)# exit! Step 2: Configure the Port-Channel interface itselfSW1(config)# interface port-channel 1SW1(config-if)# description Bundle-to-SW2SW1(config-if)# switchport mode trunkSW1(config-if)# switchport trunk allowed vlan 10,20,30SW1(config-if)# end! Step 3: Save and verifySW1# write memorySW1# show etherchannel summary
Three steps, and the order matters. First, the member interfaces get `channel-group 1 mode active` — that command creates the Port-Channel interface automatically. Then you configure the Port-Channel itself (VLANs, trunk mode, descriptions). Finally, save and verify.
Anything you configure on a member interface AFTER joining the bundle may not take effect — the Port-Channel becomes the authority. Best practice: configure member interfaces minimally (mode, channel-group), then configure the Port-Channel with the real settings.
The output tells you everything. `Po1(SU)` — the Port-Channel is up, in use, and Switchport (Layer 2). All four member ports show `(P)` — bundled. If any showed `(I)` for stand-alone, the port failed to join the bundle. If any showed `(D)`, the physical link is down.
| Flag | Meaning | Typical cause |
|---|---|---|
| P | Bundled — good | Normal operation |
| I | Stand-alone — not in bundle | Config mismatch, one-sided config, or protocol mismatch |
| D | Down | Physical link failure or admin shutdown |
| s | Suspended | Member doesn't match bundle requirements |
| H | Hot-standby | LACP with more than 8 links; standby waits |
| M | Minimum links not met | Below configured minimum for the bundle to be up |
| u | Unsuitable | Port has features incompatible with bundling |
Any mismatch and the port won't join the bundle. Cisco is usually helpful — the port ends up in `I` (stand-alone) or `s` (suspended) state, and the logs will tell you why. Look at `show etherchannel port-channel` for the specific reason.
Configure an EtherChannel in a lab with LACP active/active. Then disconnect one member link and watch `show etherchannel summary` — the port goes to `(D)` but the bundle stays up. That's the resilience you're paying for.
Finish the lesson once you have worked through the material. This awards ★ 15 XP.