EtherChannel takes multiple physical links between two switches and bundles them into a single logical link with the combined bandwidth. STP sees the bundle as one link, so no loop. Hashing distributes traffic across the member links. LACP (Link Aggregation Control Protocol) is the IEEE standard for negotiating these bundles. This lab looks at the LACP EtherChannel already configured between SW1 and SW2 in the reference lab and shows you how to read its state.
What you will learn
- The structure of an EtherChannel: logical Port-channel interface + member physical interfaces
- How LACP forms a bundle when both ends agree
- The flags in
show etherchannel summaryoutput and what they mean - The LACP modes: active (sends LACPDUs) vs passive (responds only)
- How to read
show lacp neighbor
What this lab does NOT cover
- PAgP (Cisco's proprietary equivalent) - next lab, na-07
- Layer 3 EtherChannel (used between routers)
- EtherChannel load-balancing algorithms beyond a mention
Topology
Download the STP+VLAN Reference Lab .yaml
Drop this into CML's Import dialog. Three IOSvL2 switches in a triangle with VLANs 10/20/99, dot1q trunks, rapid-PVST root election, and an LACP EtherChannel between SW1 and SW2.
The reference lab already has SW1-Gi0/3 and SW2-Gi0/3 bundled as Po1 with LACP active mode.
