LogoفارسیFA

Hands-On Lab: Configuring, Verifying, and Troubleshooting EtherChannel (Static/PAgP/LACP)

This hands-on lab bundles two physical links between switches into a single logical EtherChannel using static, PAgP, and LACP modes in turn, verifies each bundle forms correctly, and demonstrates the mismatched-mode failure that prevents a bundle from forming.

EtherChannel ConfigurationLACP and PAgP ModesPort-Channel Verification

~3 min read · Updated Sep 22, 2026

Lab Objective

Bundle two physical links between two switches into a single EtherChannel using static mode, then reconfigure the same bundle using PAgP, then LACP, verifying successful formation each time, and finally observe what happens when the two sides use mismatched modes.

Lab Purpose

EtherChannel combines multiple physical links into one logical interface, providing both aggregated bandwidth and Spanning Tree-transparent failover. Knowing all three formation methods — and recognizing a mode mismatch quickly — is essential, since the wrong combination silently prevents a bundle from forming.

Lab Topology

Switch1 ---- Gi1/0/1, Gi1/0/2 ---- Switch2

Two physical links to be bundled into
Port-channel 1

Task 1: Configure a Static EtherChannel

Bundle Gi1/0/1 and Gi1/0/2 into Port-channel 1 using static (unconditional) mode on both switches.

Task 2: Verify the Static Bundle

Confirm both member ports show as bundled (P) in the channel group.

Task 3: Reconfigure Using PAgP

Remove the static configuration and reconfigure using PAgP with desirable mode on both switches.

Task 4: Reconfigure Using LACP

Remove the PAgP configuration and reconfigure using LACP with active mode on both switches.

Task 5: Introduce a Mode Mismatch

Set Switch1 to LACP active while leaving Switch2 on PAgP desirable, and observe the resulting failure.

Solution and Verification

Switch1(config)# interface range gigabitethernet1/0/1-2
Switch1(config-if-range)# channel-group 1 mode on

Switch2(config)# interface range gigabitethernet1/0/1-2
Switch2(config-if-range)# channel-group 1 mode on

Switch1# show etherchannel summary

Group  Port-channel  Protocol   Ports
------+-------------+-----------+-----------------------
1      Po1(SU)       -          Gi1/0/1(P)  Gi1/0/2(P)
-- "-" for protocol confirms static mode
-- (no negotiation protocol used), and (P)
-- confirms both ports are bundled and active

Switch1(config)# interface range gigabitethernet1/0/1-2
Switch1(config-if-range)# no channel-group 1 mode on
Switch1(config-if-range)# channel-group 1 mode desirable

Switch2(config)# interface range gigabitethernet1/0/1-2
Switch2(config-if-range)# no channel-group 1 mode on
Switch2(config-if-range)# channel-group 1 mode desirable

Switch1# show etherchannel summary
Group  Port-channel  Protocol   Ports
1      Po1(SU)       PAgP       Gi1/0/1(P)  Gi1/0/2(P)

Switch1(config)# interface range gigabitethernet1/0/1-2
Switch1(config-if-range)# no channel-group 1 mode desirable
Switch1(config-if-range)# channel-group 1 mode active

Switch2(config)# interface range gigabitethernet1/0/1-2
Switch2(config-if-range)# no channel-group 1 mode desirable
Switch2(config-if-range)# channel-group 1 mode active

Switch1# show etherchannel summary
Group  Port-channel  Protocol   Ports
1      Po1(SU)       LACP       Gi1/0/1(P)  Gi1/0/2(P)

Switch2(config)# interface range gigabitethernet1/0/1-2
Switch2(config-if-range)# no channel-group 1 mode active
Switch2(config-if-range)# channel-group 1 mode desirable

Switch1# show etherchannel summary

Group  Port-channel  Protocol   Ports
1      Po1(SD)       LACP       Gi1/0/1(I)  Gi1/0/2(I)
-- (I) means "individual" -- the ports failed
-- to bundle, since LACP active and PAgP
-- desirable are incompatible negotiation
-- protocols that cannot form a channel together

Key Takeaway

The show etherchannel summary output's port flag is the fastest diagnostic check: (P) confirms a port successfully bundled, while (I) confirms it remains individual — almost always caused by a mode or protocol mismatch between the two switches, exactly as demonstrated when mixing LACP and PAgP.

Written & researched by Dr. Shahin Siami

Related Articles

Hands-On Lab: Configuring Static Routing via IP Addresses

This hands-on lab configures static routes using a next-hop IP address rather than an outgoing interface, the generally preferred syntax, and compares the resulting routing table entry against the interface-based approach from the previous lab.

Continue

Hands-On Lab: Configuring Static Routing via Interfaces

This hands-on lab configures static routes using an outgoing interface rather than a next-hop IP address, demonstrating this approach's suitability for point-to-point links and its important limitation on multi-access networks.

Continue

Hands-On Lab: Installing a Wireless LAN Controller

This hands-on lab performs the initial setup of a Wireless LAN Controller, joins a lightweight access point to it, and creates a centrally managed WLAN, demonstrating the controller-based architecture that scales far beyond standalone access points.

Continue

Hands-On Lab: Installing a Wireless Access Point

This hands-on lab covers physically connecting and performing the initial configuration of a standalone wireless access point, including setting up an SSID, applying WPA3 security, and verifying wireless clients can associate and reach the wired network.

Continue

Hands-On Lab: Configuring and Allowing Inter-VLAN Routing — SVI

This hands-on lab configures inter-VLAN routing using Switch Virtual Interfaces on a Layer 3 switch, enabling IP routing directly on the switch itself and comparing this approach against the router-on-a-stick method from the previous lab.

Continue

Hands-On Lab: Configuring Inter-VLAN Routing (Router on a Stick)

This hands-on lab configures inter-VLAN routing using a single router interface divided into subinterfaces, connecting to a switch trunk to route traffic between two VLANs through one physical link.

Continue
Previous ArticleNext Article