Labs / networking

LACP EtherChannel Trunk Between Two Switches

intermediate EVE-NG / Cisco IOS L2 switches etherchannellacptrunk
LAB TOPOLOGY

EtherChannel / LACP Lab

Multiple physical links · one logical Port-Channel

ACCESSNICE1/0Po1 MEMBERE0/0E0/0Po1 MEMBERE0/1E0/1Po1 MEMBERE0/2E0/2ACCESSE1/0NICPC1LAN A192.168.10.10/24SW1LACP ACTIVESW2LACP ACTIVEPC2LAN B192.168.10.20/24
Topology note:Member links must match key Layer-2 parameters before the bundle forms correctly.

Scenario

SW1 and SW2 have three physical Ethernet links between them. Instead of letting STP block redundant links, bundle E0/0, E0/1 and E0/2 into one logical Port-Channel1 using LACP. The supplied lab uses these exact member interfaces and then makes the bundle a trunk.

Success condition

show etherchannel summary should show Po1 formed and the intended member interfaces bundled. VLAN traffic should cross the logical port-channel.

Baseline

SW1# show interfaces status
SW1# show etherchannel summary
SW1# show interfaces trunk

Repeat on SW2.

Step 1 — SW1 LACP bundle

SW1# configure terminal
SW1(config)# interface range ethernet 0/0-2
SW1(config-if-range)# channel-protocol lacp
SW1(config-if-range)# channel-group 1 mode active
SW1(config-if-range)# exit
SW1(config)# interface port-channel 1
SW1(config-if)# switchport trunk encapsulation dot1q
SW1(config-if)# switchport mode trunk
SW1(config-if)# end

Step 2 — SW2 LACP bundle

SW2# configure terminal
SW2(config)# interface range ethernet 0/0-2
SW2(config-if-range)# channel-protocol lacp
SW2(config-if-range)# channel-group 1 mode active
SW2(config-if-range)# exit
SW2(config)# interface port-channel 1
SW2(config-if)# switchport trunk encapsulation dot1q
SW2(config-if)# switchport mode trunk
SW2(config-if)# end

Some IOS images do not accept switchport trunk encapsulation dot1q because 802.1Q is already the only supported encapsulation. If your image rejects only that line, continue with switchport mode trunk.

Step 3 — Verify LACP and trunk state

SW1# show etherchannel summary
SW1# show interfaces port-channel 1
SW1# show interfaces trunk
SW1# show lacp neighbor

Run the same checks on SW2. Do not accept “commands were entered” as success; confirm the bundle state.

Break it

On SW2, change one member interface so its Layer-2 settings no longer match the bundle. Check show etherchannel summary. Which member stops participating? Restore matching configuration and verify it rejoins.

Why this lab matters

EtherChannel is not three independent forwarding links. STP sees the logical port-channel as one link while LACP manages compatible physical members.

Reference

Based on Task 3 of the supplied CCNA All LABS PDF: E0/0-E0/2, LACP active mode and trunking. Explanations and troubleshooting exercise are AddySec original content.