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.
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
SW1 SW2 ==== ==== Gi0/1 ━━━━ Gi0/1 Po1 (Static) Gi0/2 ━━━━ Gi0/2 Gi0/3 ━━━━ Gi0/3 Po2 (LACP) Gi0/4 ━━━━ Gi0/4 Gi0/5 ━━━━ Gi0/5 Po3 (PAgP) Gi0/6 ━━━━ Gi0/6
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# 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# 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
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.
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. You will configure this on Gi0/3–0/4 using Port-Channel 2.
SW1(config)# interface range Gi0/3 - 4 SW1(config-if-range)# channel-group 2 mode active SW1(config-if-range)# exit SW1(config)# interface port-channel 2 SW1(config-if)# switchport mode trunk
SW2(config)# interface range Gi0/3 - 4 SW2(config-if-range)# channel-group 2 mode passive SW2(config-if-range)# exit SW2(config)# interface port-channel 2 SW2(config-if)# switchport mode trunk
SW1# show lacp neighbor SW1# show etherchannel 2 summary
Task 3: PAgP EtherChannel (Cisco Proprietary)
PAgP is Cisco's proprietary channel negotiation protocol. Desirable mode actively initiates negotiation; auto mode only responds. Configure PAgP on Gi0/5–0/6, Port-Channel 3.
SW1(config)# interface range Gi0/5 - 6 SW1(config-if-range)# channel-group 3 mode desirable SW1(config-if-range)# exit SW1(config)# interface port-channel 3 SW1(config-if)# switchport mode trunk
SW2(config)# interface range Gi0/5 - 6 SW2(config-if-range)# channel-group 3 mode auto SW2(config-if-range)# exit SW2(config)# interface port-channel 3 SW2(config-if)# switchport mode trunk
Task 4: Load-Balancing Method
EtherChannel load-balancing is configured globally. Change the hash algorithm and observe which physical port carries each flow.
! 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 |
| 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 |