Cisco NX-OS Port-Channel / LACP

Cisco NX-OSIntermediate

LACP port-channel configuration for Cisco Nexus switches. Supports L2 trunk/access and L3 routed port-channels, with optional vPC membership.

↓ example.txt

What is it?

NX-OS LACP port-channels bundle multiple physical interfaces into a single logical interface for bandwidth aggregation and redundancy, same as Cisco IOS. The key NX-OS difference: 'feature lacp' must be enabled first, NX-OS uses 'port-channel' (lowercase with hyphen) instead of 'Port-channel', and port-channels can be members of a vPC domain. In data center leaf switches, most server connections use LACP port-channels — dual-homed to one switch (standard port-channel) or dual-homed across two switches (vPC port-channel).

✓ When to use

·Server connections that need more than 10G or 25G bandwidth
·Dual-homed server connections for redundancy (use vPC if connecting to two switches)
·Spine-to-leaf uplinks where maximizing bandwidth is critical
·Any connection where link redundancy without STP blocking is needed

✗ When NOT to use

·Do not mix different speed interfaces in one port-channel — all members must be the same speed
·Do not use 'mode on' (static) for production server connections — use LACP 'active' so failures are detected

How it compares

vs Cisco IOS port-channelSame LACP protocol. NX-OS requires 'feature lacp' first. NX-OS port-channels can be assigned a 'vpc <id>' to participate in a vPC domain — no IOS equivalent.

vs vPC (Virtual Port-Channel)Standard port-channel connects to one NX-OS switch. vPC connects to two NX-OS switches that form a vPC domain — the server sees one logical port-channel but connects to two physical switches for better redundancy.

Prerequisites

→'feature lacp' must be enabled before channel-group commands will work
→Both member interfaces must have identical speed, duplex, and switchport configuration
→For vPC port-channels: the vPC domain must be configured first (see vpc template)
→NX-OS requires 'no switchport' on L3 port-channels — they default to L2

Config Generator

Hostname *

Port-Channels

Member Interfaces

Verification commands

show port-channel summary

Show all port-channels and member interface state

Expected: Port-channel shows 'U' (in use). Members show 'P' (bundled). Members showing 'I' (individual) are not bundled.

show lacp neighbor

Show LACP partner information from the connected device

Expected: Shows neighbor's system ID, port priority, and LACP state for each member interface

show interface port-channel<id> counters

Show traffic counters per port-channel

Expected: Non-zero input/output packets. CRC errors indicate physical layer problems on member links.

Debug commands

show lacp internal

Show LACP state machine status for all port-channel members

Common mistakes & fixes

⚡ Members showing 'I' (individual) instead of 'P' (bundled)

Cause: LACP mismatch (both passive), interface configuration inconsistency, or peer not responding to LACP PDUs

Fix: Verify 'feature lacp' is enabled. Set at least one side to 'mode active'. Check interface speed/duplex match. Verify peer switch has LACP enabled.

⚡ vPC port-channel member not bundling

Cause: vPC ID mismatch between the two vPC peers, or port-channel config inconsistency

Fix: Verify both vPC peers have identical port-channel config for the same vPC ID. Check 'show vpc consistency-parameters' for differences.