![LACP vs PAgP: Cisco EtherChannel Types Explained with CLI & EVE-NG Lab [2025]. [CCNP ENTERPRISE]](https://networkjourney.com/wp-content/uploads/2025/06/LACP-vs-PAgP_-Cisco-EtherChannel-Types-Explained-with-CLI_networkjourney.png)
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.
Table of Contents
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:
- Manual (On) – No negotiation protocol. Both ends must be configured as “on”.
- PAgP (Port Aggregation Protocol) – Cisco proprietary.
- 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
| Feature | LACP (IEEE 802.3ad) | PAgP (Cisco) | Manual (“On”) |
|---|---|---|---|
| Vendor Support | Multi-vendor | Cisco-only | Cisco, but no protocol |
| Negotiation | Yes | Yes | No |
| Modes | Active / Passive | Auto / Desirable | On / On |
| Recommended Usage | Preferred (standard) | Legacy Cisco setups | Avoid (no protection) |
| Misconfig Detection | Yes | Yes | No |
| Number of Links Supported | 16 (max 8 active) | 8 | 8 |
| Flexibility | High | Medium | Low |
| Use Case | Mixed environments | Pure Cisco environments | Labs or manual testing |
Essential CLI Commands – EtherChannel Setup
| Task | Command Example | Notes |
|---|---|---|
| Check port channel status | show etherchannel summary | Displays bundle ID, mode, status |
| Show detailed port-channel info | show etherchannel <id> detail | Protocol type, active interfaces |
| Enable LACP on interface | channel-group 1 mode active | Active mode (LACP) |
| Enable PAgP on interface | channel-group 1 mode desirable | Desirable mode (PAgP) |
| Manual EtherChannel | channel-group 1 mode on | No negotiation |
| View physical interface info | show interfaces status | Check links |
| View logical port-channel interface | show interface port-channel 1 | Stats and errors |
| Check errors or misconfig | show spanning-tree / debug etherchannel | Verify compatibility |
Real-World Use Case
| Environment Type | Scenario | Recommended Protocol |
|---|---|---|
| Campus Core–Distribution | 4x10Gbps uplinks between switches | LACP (standard, stable) |
| Cisco-only Access Switches | 2x1Gbps uplinks in older catalyst devices | PAgP (backward support) |
| WAN Router to Core Switch | Single vendor (Cisco) setup | LACP (active-passive) |
| Multi-vendor (Cisco + Juniper) | Mixed network topology | LACP only |
| Lab with no negotiation needed | Force link aggregation | Manual (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
| Symptom | Cause | Solution/Command |
|---|---|---|
| Port-channel not forming | Mode mismatch (e.g., passive/passive) | Use active on at least one end |
| Interfaces in different VLANs | Access/trunk mismatch | Ensure both sides match config |
| Links up but traffic drops | Not in EtherChannel bundle | Use show etherchannel summary |
| Ports in err-disabled | Incompatible settings or loops | Use show log and errdisable recovery |
| Bundle forms but flaps | Inconsistent speed/duplex on links | Use 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 Mode | Description |
|---|---|
| Active | Actively negotiates with the other end to form an EtherChannel |
| Passive | Responds 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 Mode | Description |
|---|---|
| Desirable | Actively tries to form a channel |
| Auto | Waits 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-ipsrc-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:
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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