Cisco EtherChannel and LACP Commands: Check Bundles and Members

Read-only commands #

show etherchannel summary

show etherchannel 1 detail

show lacp 1 neighbor

show lacp 1 counters

show interfaces Port-channel1

show interfaces GigabitEthernet1/0/23

show interfaces GigabitEthernet1/0/24

show etherchannel load-balance

Key flags #

Common summary flags include P for a bundled member, s for suspended, I for standalone, S for a Layer 2 channel and R for a Layer 3 channel. U identifies a channel in use. Use the printed legend because platforms and releases can add more flags.

Workflow #

1. Write down the expected port-channel number and member interfaces at both ends. Local and remote group numbers need not be identical, so use the physical link mapping as your anchor.
2. Compare the expected member count with the summary. Inspect missing, suspended or standalone members individually before investigating application performance.
3. Inspect LACP neighbor information. Check whether the physical members lead to the intended partner system. A valid neighbor on one cable does not validate the rest of the cabling.
4. Take two counter snapshots if LACP exchange is uncertain. Compare transmitted and received activity at each end without clearing the existing evidence.
5. Verify the logical interface's Layer 2 or Layer 3 role. For a switched bundle, continue with trunk and STP checks on the port-channel. For a routed bundle, continue with route lookup and neighbor resolution.

Why traffic may be uneven #

EtherChannel distributes traffic according to a selection algorithm; it does not promise to split one application flow equally across all member links. A single large transfer may use one member while other members remain quiet. Read the configured load-balancing method and compare multiple flows before declaring a failed member.

Do not confuse a correctly negotiated bundle with a correctly configured service. LACP can establish while a required VLAN is missing elsewhere on the path. Equally, an empty LACP-neighbor display needs context if the channel uses a static mode rather than LACP.

Evidence to save #

Keep both summaries, the member mapping, partner information and synchronized interface counters. This supports a focused escalation without bouncing the bundle or disrupting the traffic that still works.

Useful tools and references #

• Bandwidth and transfer time calculator: Estimate transfer duration against the capacity available to one flow; do not automatically use the sum of all bundle members.