interface port-channel [id]
Creates or enters the configuration mode for an EtherChannel port-channel interface, used to bundle multiple physical Ethernet links into a single logical link for redundancy and increased bandwidth.
interface port-channel [id]When to Use This Command
- Aggregating two or more trunk links between switches to increase uplink bandwidth and provide redundancy.
- Combining access ports connecting a server to a switch for higher throughput and fault tolerance.
- Configuring a Layer 3 EtherChannel between a router and a switch to provide a high-bandwidth routed link.
- Setting up a cross-stack EtherChannel across multiple switches in a stack for resilient connectivity.
Command Examples
Create and configure a Layer 2 EtherChannel interface
interface port-channel 1Switch(config)#interface port-channel 1 Switch(config-if)#
The command enters interface configuration mode for port-channel 1. If the interface does not exist, it is created. The prompt changes to (config-if)# indicating you are now configuring that logical interface.
Configure a Layer 3 EtherChannel with an IP address
interface port-channel 10
ip address 192.168.1.1 255.255.255.0
no shutdownSwitch(config)#interface port-channel 10 Switch(config-if)#ip address 192.168.1.1 255.255.255.0 Switch(config-if)#no shutdown Switch(config-if)#
After entering port-channel 10, an IP address is assigned to the logical interface, making it a routed port. The 'no shutdown' ensures the interface is administratively up. The output shows each command being accepted without error.
Understanding the Output
The output of 'interface port-channel [id]' is minimal: it simply changes the CLI prompt to indicate you are in interface configuration mode for that port-channel. There is no detailed output; the command is used to enter configuration context. To verify the EtherChannel, use 'show etherchannel summary' or 'show interfaces port-channel [id]'. In those outputs, look for the port-channel status (up/down), the member ports, and the protocol (LACP or PAgP). A healthy EtherChannel shows all member ports in the same bundle and the port-channel interface in an up/up state. Watch for mismatched port speeds, duplex, or VLAN configurations which can cause the channel to fail.
CCNA Exam Tips
CCNA exam tip: Remember that the port-channel number must match on both sides of the link for the EtherChannel to form.
CCNA exam tip: You must assign physical interfaces to the port-channel using 'channel-group [number] mode [active|passive|desirable|auto|on]' under each physical interface.
CCNA exam tip: The exam may test that all physical interfaces in the channel must have the same speed, duplex, and VLAN configuration (if Layer 2).
CCNA exam tip: For Layer 3 EtherChannels, you must issue 'no switchport' on the port-channel interface before assigning an IP address.
Common Mistakes
Mistake 1: Forgetting to assign physical interfaces to the port-channel with the 'channel-group' command, resulting in the port-channel being empty and down.
Mistake 2: Configuring the port-channel interface with an IP address without first using 'no switchport' on a Layer 3 switch, causing the IP to be rejected.
Mistake 3: Using inconsistent EtherChannel modes (e.g., one side set to 'active' and the other to 'desirable' with PAgP) leading to negotiation failure.
Related Commands
channel-group [id] mode [mode]
Assigns an interface to an EtherChannel bundle with a specified channel-group number and mode (active, passive, or desirable) to aggregate multiple physical links into a single logical link for redundancy and increased bandwidth.
show etherchannel summary
Displays the status and configuration of all EtherChannel interfaces on the switch, used to verify channel bundling, port membership, and protocol state.
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