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Cisco NX-OS Port-Channel / LACP

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

ExpectedPort-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

ExpectedShows 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

ExpectedNon-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

SymptomMembers showing 'I' (individual) instead of 'P' (bundled)

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

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

SymptomvPC port-channel member not bundling

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

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

Further learning

Recommended books to go deeper on this topic.

CCNA 200-301 Official Cert Guide Library

Wendell Odom · Cisco Press · EtherChannel, LACP, PAgP — fundamentals and configuration

Kindle ↗Hardcover ↗

CCNP Enterprise Core ENCOR 350-401 Official Cert Guide

Brad Edgeworth et al. · Cisco Press · Port-channel design, load balancing, compatibility requirements