EtherChannel can be negotiated by two different protocols: Cisco's proprietary PAgP (Port Aggregation Protocol) or the IEEE standard LACP (Link Aggregation Control Protocol, 802.3ad). LACP is the modern default because it interoperates with everyone. PAgP only works between Cisco switches. This lab compares them side by side and shows when you might (rarely) still use PAgP.
What you will learn
- The two protocols and their key differences
- The mode keywords for each (LACP: active/passive; PAgP: desirable/auto)
- How to read
show etherchannel summaryto identify which protocol is in use - The interoperability rule: you cannot mix PAgP on one end with LACP on the other
- When PAgP is still seen in production and why it is being phased out
What this lab does NOT cover
- Layer 3 EtherChannel (different config, same protocol options)
- Multi-chassis EtherChannel (vPC, MLAG, VSS)
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.
