How to Configure EtherChannel on Cisco Switches Using LACP
Learn how to configure LACP EtherChannel on Cisco IOS switches step by step. This guide covers requirements, configuration commands, trunk setup, verification, and troubleshooting to build a stable and redundant switch uplink using Port-Channel.
In this lab-focused guide, you’ll learn how to configure LACP EtherChannel (Port-Channel 1) between two Cisco IOS switches using clean and reliable configuration steps. This method is production-safe and certification-friendly (CCNA/CCNP).
What You’ll Build
- Two switches connected using two uplink ports (Gi1/0/1–2)
- Create Port-Channel 1 using LACP (mode active)
- Convert the Port-Channel to a trunk for VLANs
- Verify and troubleshoot the EtherChannel
Requirements
- Both switches must support IEEE 802.3ad (LACP)
- Interfaces used must:
- Match speed and duplex
- Be Layer 2 switchports (not routing ports)
- Use the same trunk settings on both ends
- Minimum of two links, maximum of 8 active LACP links
Step 1: Clean Up Interfaces (Recommended Before Config)
Before configuring EtherChannel, remove any old settings from the member interfaces.
Run on both switches:
default interface range gi1/0/1 - 2
no interface port-channel 1
Tip: This prevents errors from leftover configs during bundling.
Step 2: Configure Member Interfaces
Enable switchport mode and assign interfaces to channel-group 1 using LACP active mode.
Switch A
interface range gi1/0/1 - 2
switchport
channel-group 1 mode active
description Member links to Switch B
no shutdown
Switch B
interface range gi1/0/1 - 2
switchport
channel-group 1 mode active
description Member links to Switch A
no shutdown
Warning: Do not configure VLANs or trunking here; do it on the Port-Channel only.
Step 3: Configure the Port-Channel Interface
Once LACP forms the bundle, configure Port-Channel 1 as a trunk link.
Switch A
interface port-channel1
switchport
switchport mode trunk
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20,30
description LACP Port-Channel to Switch B
Switch B
interface port-channel1
switchport
switchport mode trunk
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20,30
description LACP Port-Channel to Switch A
Tip: Always match trunk settings on both sides to prevent VLAN mismatch or loops.
Step 4: Verify EtherChannel
Use these commands to confirm your configuration:
| Purpose | Command | Expected Result |
|---|---|---|
| Check EtherChannel status | show etherchannel summary | Po1 = SU, members = P (bundled) |
| View LACP neighbors | show lacp neighbor | Shows partner switch ports |
| Check trunking | show interfaces trunk | Po1 listed as trunk |
| Inspect port-channel | show interfaces port-channel 1 | Line protocol up |
Optional: Load Balancing (Advanced)
Cisco switches choose how traffic is shared across bundled links.
port-channel load-balance src-dst-ip
Other options include src-mac, dst-ip, or src-dst-port.
Full Configuration Summary
Switch A
default interface range gi1/0/1 - 2
no interface port-channel 1
interface range gi1/0/1 - 2
switchport
channel-group 1 mode active
no shutdown
interface port-channel1
switchport
switchport mode trunk
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20,30
description LACP Po1 to Switch B
Switch B
default interface range gi1/0/1 - 2
no interface port-channel 1
interface range gi1/0/1 - 2
switchport
channel-group 1 mode active
no shutdown
interface port-channel1
switchport
switchport mode trunk
switchport trunk native vlan 99
switchport trunk allowed vlan 10,20,30
description LACP Po1 to Switch A
Troubleshooting EtherChannel (Common Errors)
| Issue | Cause | Fix |
|---|---|---|
Ports show (I) individual state | Trunk settings or speed mismatch | Check both sides match |
| Port-Channel down | Old config left behind | Use default interface cleanup |
| VLANs not passing | Trunk missing VLANs | Check allowed vlan |
| Load not balanced | Single flow pinned | Try load-balance src-dst-ip |
| Suspended port | Mismatch or STP issue | Verify show spanning-tree |
Useful Commands:
show etherchannel summary
show lacp neighbor
show interfaces port-channel 1
show interfaces status
show spanning-tree interface port-channel 1
Final Notes
LACP EtherChannel is a reliable way to:
✅ Increase bandwidth
✅ Add redundancy
✅ Prevent spanning-tree blocking on uplinks
By keeping configuration simple, clean, and consistent, you can build stable switch-to-switch uplinks in labs and production networks.
HSRP FAQ
Q: What is HSRP in Cisco?
HSRP (Hot Standby Router Protocol) is a Cisco redundancy protocol used to provide gateway failover between two or more routers or Layer 3 switches.
Q: How does HSRP work?
HSRP creates a virtual gateway IP shared between devices. One router is Active, the other is Standby. If the Active fails, the Standby takes over automatically.
Q: What is the default HSRP priority?
The default priority is 100. Higher priority becomes Active. For example: standby 1 priority 110.
Q: What is preempt in HSRP?preempt lets a higher-priority router take back the Active role once it comes back online.
Q: What is HSRP used for?
It prevents gateway failure. If one router goes down, users stay online because traffic automatically switches to the backup.
Q: What are HSRP hello and hold timers?
By default, HSRP sends hello every 3 seconds and uses a 10-second hold timer before declaring failure.
Q: Can HSRP run on Layer 3 switches?
Yes, HSRP works on Cisco multilayer switches (like Catalyst 3560/3750/3850/9300) as long as IP routing is enabled.
Q: What ports does HSRP use?
HSRP uses UDP port 1985 for communication between routers in the same group.
Q: How do I check HSRP status?
Use:
show standby
This shows Active/Standby state, timers, and priority.
Q: Can HSRP support VLANs?
Yes, HSRP is commonly used with SVIs (Switch Virtual Interfaces) to provide default gateway redundancy per VLAN.
