23.2.4 Configuring Port Channel Interfaces

A port channel interface is used to set the functions that operate on a channel group.

A port channel interface is set up manually by using configuration commands or generated automatically when the channel-group mode command is executed in Ethernet interface configuration mode.

<Structure of this section>

(1) Relationship between Port Channel Interface and Ethernet Interface

A port channel interface is used to configure the functionality that operates on a channel group. The same functionality can also be configured from the Ethernet interface in configuration mode. Some of the commands provided by these interfaces are related as follows:

The settings of the related commands of the port channel and Ethernet interfaces must match.
If the channel-group mode command is specified by using an Ethernet interface when a port channel interface has not been set up, the port channel interface is automatically generated. At this time, related commands must not be specified in the Ethernet interface in which the channel-group mode command is specified.
If the channel-group mode command is specified by using an Ethernet interface when a port channel interface has already been set up, the settings of the related commands must match.
If a related command is set by using a port channel interface, the setting is also applied to a related command registered in an Ethernet interface by using the channel-group mode command.

The following table describes the port channel interface commands whose settings must be identical with the settings of the related Ethernet interface commands.

Table 23-3: Commands related to port channel interfaces
Functionality	Command
VLAN	switchport mode
	switchport access
	switchport trunk
	switchport protocol
	switchport mac
	switchport vlan mapping
	switchport vlan mapping enable
Spanning Tree Protocols	spanning-tree portfast
	spanning-tree bpdufilter
	spanning-tree bpduguard
	spanning-tree guard
	spanning-tree link-type
	spanning-tree port-priority
	spanning-tree cost
	spanning-tree vlan port-priority
	spanning-tree vlan cost
	spanning-tree single port-priority
	spanning-tree single cost
	spanning-tree mst port-priority
	spanning-tree mst cost
DHCP Snooping	ip dhcp snooping trust
	ip arp inspection trust
	ip verify source
L2 Loop Detection	loop-detection
Layer 2 Authentication	authentication arp-relay
	authentication force-authorized vlan
	authentication ip access-group
	authentication logout linkdown
	authentication mac access-group
	authentication max-user(interface)
IEEE802.1X	dot1x port-control
Web Authentication	web-authentication port
MAC-based Authentication	mac-authentication dot1q-vlan force-authorized
MAC-based Authentication	mac-authentication port
Multistep authentication	authentication multi-step

(2) Settings for functions that operate on channel groups

Points to note: The port channel interface is used to set up the VLAN, Spanning Tree Protocols, and other functionality used for channel group operations. In this example, you set up a trunk port.

Command examples

(config)# interface range gigabitethernet 1/0/1-2

(config-if-range)# channel-group 10 mode on

(config-if-range)# exit

Adds ports 1/0/1 and 1/0/2 to channel group 10 in static mode. The port channel interface for channel group 10 is automatically generated.
(config)# interface port-channel 10

Switches channel group 10 to port channel interface configuration mode.
(config-if)# switchport mode trunk

Sets channel group 10 as a trunk port.

(3) Port Channel Interface shutdown

Points to note: When shutdown is set for a port channel interface, communication over all ports registered in the channel group stops. Ports in the link-up status stop communication, preserving the status.

Command examples

(config)# interface range gigabitethernet 1/0/1-2

(config-if-range)# channel-group 10 mode on

(config-if-range)# exit

Adds ports 1/0/1 and 1/0/2 to channel group 10 in static mode.
(config)# interface port-channel 10

(config-if)# shutdown

Changes the mode to port channel interface configuration mode, and sets shutdown. Channel group 10 is shut down, so communication over ports 1/0/1 and 1/0/2 stops.