LACP vs PAgP: Cisco EtherChannel Types Explained with CLI & EVE-NG Lab [2025] [CCNP ENTERPRISE]

LACP vs PAgP: Cisco EtherChannel Types Explained with CLI & EVE-NG Lab [2025]. [CCNP ENTERPRISE]

One of the most common things I hear from learners in my CCNA/CCNP classes is:
“Why does EtherChannel break sometimes even though the cables are good?”
Well, the answer often lies in how you bundle those links—whether it’s LACP or PAgP, manual or dynamic.

This post will walk you through EtherChannel basics, break down the differences between LACP and PAgP, show you real CLI commands, and even provide a mini EVE-NG lab for practice. If you’re preparing for exams or building a rock-solid LAN design—this is your complete guide.


Theory in Brief – Understanding EtherChannel, LACP, and PAgP

EtherChannel is a technology that allows the bundling of multiple physical links between switches or routers into a single logical interface. This increases bandwidth, provides redundancy, and helps avoid loops without relying on Spanning Tree Protocol to block links.

There are three ways to create an EtherChannel:

  1. Manual (On) – No negotiation protocol. Both ends must be configured as “on”.
  2. PAgP (Port Aggregation Protocol) – Cisco proprietary.
  3. LACP (Link Aggregation Control Protocol) – IEEE standard (802.3ad).

PAgP is only used in Cisco environments, while LACP is the industry standard—making it the better choice when dealing with multi-vendor setups.

Both LACP and PAgP can negotiate channel parameters and prevent misconfigurations. However, they differ in modes, compatibility, and flexibility.


Summary – LACP vs PAgP vs Manual

FeatureLACP (IEEE 802.3ad)PAgP (Cisco)Manual (“On”)
Vendor SupportMulti-vendorCisco-onlyCisco, but no protocol
NegotiationYesYesNo
ModesActive / PassiveAuto / DesirableOn / On
Recommended UsagePreferred (standard)Legacy Cisco setupsAvoid (no protection)
Misconfig DetectionYesYesNo
Number of Links Supported16 (max 8 active)88
FlexibilityHighMediumLow
Use CaseMixed environmentsPure Cisco environmentsLabs or manual testing

Essential CLI Commands – EtherChannel Setup

TaskCommand ExampleNotes
Check port channel statusshow etherchannel summaryDisplays bundle ID, mode, status
Show detailed port-channel infoshow etherchannel <id> detailProtocol type, active interfaces
Enable LACP on interfacechannel-group 1 mode activeActive mode (LACP)
Enable PAgP on interfacechannel-group 1 mode desirableDesirable mode (PAgP)
Manual EtherChannelchannel-group 1 mode onNo negotiation
View physical interface infoshow interfaces statusCheck links
View logical port-channel interfaceshow interface port-channel 1Stats and errors
Check errors or misconfigshow spanning-tree / debug etherchannelVerify compatibility

Real-World Use Case

Environment TypeScenarioRecommended Protocol
Campus Core–Distribution4x10Gbps uplinks between switchesLACP (standard, stable)
Cisco-only Access Switches2x1Gbps uplinks in older catalyst devicesPAgP (backward support)
WAN Router to Core SwitchSingle vendor (Cisco) setupLACP (active-passive)
Multi-vendor (Cisco + Juniper)Mixed network topologyLACP only
Lab with no negotiation neededForce link aggregationManual (on)

EVE-NG LAB – EtherChannel with LACP & PAgP

Objective:

  • Create and verify EtherChannel using both LACP and PAgP modes.
  • Identify common misconfigurations.

Topology

Both switches are Cisco IOSv Layer 2 with two physical links between them.


Configuration – LACP (Active/Passive)

! On SW1
interface range e1/1 - 2
 switchport mode trunk
 channel-group 1 mode active

! On SW2
interface range e1/1 - 2
 switchport mode trunk
 channel-group 1 mode passive

Configuration – PAgP (Desirable/Auto)

! On SW1
interface range e1/1 - 2
 switchport mode trunk
 channel-group 2 mode desirable

! On SW2
interface range e1/1 - 2
 switchport mode trunk
 channel-group 2 mode auto

Verify Results

SW1# show etherchannel summary

Output:

Group  Port-channel  Protocol    Ports
------+--------------+-----------+-----------------------------
1      Po1(SU)        LACP        Gi1/1(P) Gi1/2(P)
2      Po2(SU)        PAgP        Gi1/1(P) Gi1/2(P)

Troubleshooting Tips

SymptomCauseSolution/Command
Port-channel not formingMode mismatch (e.g., passive/passive)Use active on at least one end
Interfaces in different VLANsAccess/trunk mismatchEnsure both sides match config
Links up but traffic dropsNot in EtherChannel bundleUse show etherchannel summary
Ports in err-disabledIncompatible settings or loopsUse show log and errdisable recovery
Bundle forms but flapsInconsistent speed/duplex on linksUse show interface and align settings

FAQs – LACP vs PAgP

1. What is the primary difference between LACP and PAgP?

Answer:

  • LACP (Link Aggregation Control Protocol) is an open standard (IEEE 802.3ad) and supported across vendors.
  • PAgP (Port Aggregation Protocol) is Cisco proprietary and only works between Cisco devices.

Both protocols negotiate and manage EtherChannel groups, but LACP offers multi-vendor compatibility.


2. What modes are available in LACP and how do they work?

Answer:

LACP ModeDescription
ActiveActively negotiates with the other end to form an EtherChannel
PassiveResponds to LACP requests but does not initiate

A successful EtherChannel requires at least one side in Active mode.

Example:

channel-group 1 mode active

3. What modes are available in PAgP?

Answer:

PAgP ModeDescription
DesirableActively tries to form a channel
AutoWaits passively for PAgP messages

Just like LACP, one side must be in desirable for a channel to form:

channel-group 1 mode desirable

4. Can I manually configure EtherChannel without using LACP or PAgP?

Answer:
Yes, using on mode:

channel-group 1 mode on

This forms an EtherChannel without negotiation. It’s riskier because both ends must match exactly (same speed, duplex, allowed VLANs, etc.), or the channel won’t work.


5. What are the advantages of LACP over PAgP in enterprise networks?

Answer:

  • Vendor compatibility (not tied to Cisco)
  • Better fault tolerance with dynamic link detection
  • Supports up to 16 links (8 active, 8 standby)
  • More widely adopted in data center and multi-vendor environments

PAgP is suitable only in Cisco-only deployments.


6. How do I verify if an EtherChannel is working correctly?

Answer:
Use:

show etherchannel summary

Example output:

Group  Port-channel  Protocol    Ports
------+-------------+-----------+-------------------------
1      Po1           LACP        Gi0/1(P) Gi0/2(P)

You can also use:

show interfaces port-channel 1

To see interface status and load balancing.


7. What are common reasons an EtherChannel fails to form?

Answer:

  • Mismatched channel-group modes (e.g., both sides passive)
  • Inconsistent trunk/access mode
  • Speed/duplex mismatch
  • VLAN mismatch on trunk ports
  • Incorrect protocol (LACP vs PAgP)

Use debug pagp or debug lacp to help pinpoint issues.


8. Can I mix LACP and PAgP on the same EtherChannel?

Answer:
No. LACP and PAgP are mutually exclusive. Both sides of the link must use the same negotiation protocol, or use manual (on) mode.

If mismatched, the channel will fail and revert to individual interfaces.


9. How many physical interfaces can be bundled in LACP or PAgP?

Answer:

  • LACP: Up to 16 ports (8 active + 8 standby)
  • PAgP: Maximum of 8 active ports

Most switches limit active ports in one EtherChannel to 8, with the rest serving as backups.


10. Is EtherChannel load balancing automatic? Can I control it?

Answer:
Yes, load balancing is enabled by default, but you can control it using:

port-channel load-balance <method>

Methods include:

  • src-ip, dst-ip, src-dst-ip
  • src-mac, dst-mac, src-dst-mac

Use:

show etherchannel load-balance

To view current settings.


YouTube Lab Link

Watch the Complete CCNP Enterprise: LACP vs PAgP: Cisco EtherChannel Types Explained with CLI & EVE-NG Lab Demo & Explanation on our channel:

Class 1 CCNP Enterprise Course and Lab Introduction | FULL COURSE 120+ HRS | Trained by Sagar Dhawan
Class 2 CCNP Enterprise: Packet Flow in Switch vs Router, Discussion on Control, Data and Management
Class 3 Discussion on Various Network Device Components
Class 4 Traditional Network Topology vs SD Access Simplified

Final Note

Understanding how to differentiate and implement LACP vs PAgP: Cisco EtherChannel Types Explained with CLI is critical for anyone pursuing CCNP Enterprise (ENCOR) certification or working in enterprise network roles. Use this guide in your practice labs, real-world projects, and interviews to show a solid grasp of architectural planning and CLI-level configuration skills.

If you found this article helpful and want to take your skills to the next level, I invite you to join my Instructor-Led Weekend Batch for:

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