EtherChannel Configuration | CCNA Practice Lab

Lab Overview

In this lab you will configure EtherChannel link aggregation between two Layer-2 switches using all three negotiation modes: static (ON), LACP (IEEE 802.3ad), and PAgP (Cisco proprietary). You will verify that bundled ports appear as a single logical interface and that traffic load-balances correctly across physical member links.

Before you begin
Reset both switches to factory defaults or use a clean Packet Tracer topology file. All physical cables must be connected as shown in the topology before you issue any commands.

Network Topology

Task 1: Static EtherChannel (Mode ON)

Configure a static bundle on ports Gi0/1–0/2 between SW1 and SW2. Static mode forces the ports into the channel without sending any negotiation frames. Both sides must be set to ON.

SW1 CLI (Static Bundle)

SW1# configure terminal
SW1(config)# interface range GigabitEthernet0/1 - 2
SW1(config-if-range)# channel-group 1 mode on
SW1(config-if-range)# exit
SW1(config)# interface port-channel 1
SW1(config-if)# switchport mode trunk
SW1(config-if)# end

SW2 CLI (Static Bundle)

SW2# configure terminal
SW2(config)# interface range GigabitEthernet0/1 - 2
SW2(config-if-range)# channel-group 1 mode on
SW2(config-if-range)# exit
SW2(config)# interface port-channel 1
SW2(config-if)# switchport mode trunk
SW2(config-if)# end

Common mistake
Mismatched duplex, speed, or trunk settings on member ports will prevent the bundle from forming. Ensure all physical interfaces share identical Layer-2 config before bundling.

Key Command: Understanding no channel-group 1

In the upcoming examples (Task 2 for LACP and Task 3 for PAgP), you will execute the command: SW1(config-if-range)# no channel-group 1

Unbinds Member Ports: This command removes physical interfaces Gi0/1 and Gi0/2 from the logical bundle Port-channel 1, returning them to standalone Layer-2 switchports.
Prevents Mode Conflict Errors: Cisco IOS will reject directly switching an existing bundle from static (mode on) to dynamic negotiation (mode active or desirable). Attempting to do so without unbinding first generates an error: % Command rejected: Mode on is not compatible with mode active.
Clean State for Link Reuse: Because this lab reuses the same pair of physical cables (Gi0/1–0/2) to practice all three EtherChannel modes, running no channel-group 1 cleanly resets the negotiation state before applying a new protocol.

SW1 CLI (Verification)

SW1# show etherchannel summary
SW1# show interfaces port-channel 1
SW1# show etherchannel detail

Command	What to Confirm
show etherchannel summary	Po1 shows flags SU (layer2, in use)
show interfaces po1	Line protocol is up
show etherchannel detail	Both Gi0/1 and Gi0/2 listed as bundled

Task 2: LACP EtherChannel (IEEE 802.3ad)

LACP is the open-standard protocol for link aggregation. One side is set to active (sends LACP PDUs) and the other to passive (responds to PDUs). Both sides set to active also works. Reconfigure ports Gi0/1–0/2 using Port-Channel 1 by removing the previous static channel first.

SW1 CLI (LACP Active Side)

SW1(config)# interface range GigabitEthernet0/1 - 2
SW1(config-if-range)# no channel-group 1
SW1(config-if-range)# channel-group 1 mode active
SW1(config-if-range)# exit
SW1(config)# interface port-channel 1
SW1(config-if)# switchport mode trunk

SW2 CLI (LACP Passive Side)

SW2(config)# interface range GigabitEthernet0/1 - 2
SW2(config-if-range)# no channel-group 1
SW2(config-if-range)# channel-group 1 mode passive
SW2(config-if-range)# exit
SW2(config)# interface port-channel 1
SW2(config-if)# switchport mode trunk

SW1 CLI (Verification)

SW1# show lacp neighbor
SW1# show etherchannel 1 summary

Task 3: PAgP EtherChannel (Cisco Proprietary)

PAgP is Cisco's proprietary channel negotiation protocol. Desirable mode actively initiates negotiation; auto mode only responds. Reconfigure ports Gi0/1–0/2 for PAgP by removing the previous LACP bundle first.

SW1 CLI (PAgP Desirable)

SW1(config)# interface range GigabitEthernet0/1 - 2
SW1(config-if-range)# no channel-group 1
SW1(config-if-range)# channel-group 1 mode desirable
SW1(config-if-range)# exit
SW1(config)# interface port-channel 1
SW1(config-if)# switchport mode trunk

SW2 CLI (PAgP Auto)

SW2(config)# interface range GigabitEthernet0/1 - 2
SW2(config-if-range)# no channel-group 1
SW2(config-if-range)# channel-group 1 mode auto
SW2(config-if-range)# exit
SW2(config)# interface port-channel 1
SW2(config-if)# switchport mode trunk

SW1 CLI (Verification)

SW1# show pagp neighbor
SW1# show etherchannel 1 summary

Task 4: Load-Balancing Method

EtherChannel load-balancing is configured globally. Change the hash algorithm and observe which physical port carries each flow.

SW1 CLI (Load-Balance)

! Default is src-mac — change to src-dst-ip for IP-based hashing
SW1(config)# port-channel load-balance src-dst-ip
SW1# show etherchannel load-balance

Method	Hash Input	Best Use-Case
src-mac	Source MAC	Many hosts, same destination
dst-mac	Destination MAC	One source, many destinations
src-dst-ip	Src IP XOR Dst IP	Routed / inter-VLAN traffic
src-dst-mac	Src MAC XOR Dst MAC	Mixed switched environments

Mode Compatibility — Quick Reference

Protocol	Mode	Mode	Compatibility
LACP	active	active	Yes
LACP	active	passive	Yes
LACP	passive	passive	No
PAgP	desirable	desirable	Yes
PAgP	desirable	auto	Yes
PAgP	auto	auto	No
Static	on	on	Yes
Static	on	active/passive	No

Review Questions

Q1	What happens if you set one side to mode `on` and the other side to mode `active` (LACP)?
Q2	Can PAgP and LACP be used simultaneously on the same EtherChannel bundle? Explain why or why not.
Q3	You have 4 physical links in a bundle. A single host sends all traffic to a single server. How many physical links carry that flow? Why?
Q4	List the flags you would expect to see in `show etherchannel summary` for a healthy LACP bundle on a Layer-2 switch.

Next Lab: Lab 8: Rapid Spanning Tree Protocol (RSTP)