Cisco Cisco IOS Software Release 12.2(27)SBC

When port channel interfaces are configured improperly with LACP, they are disabled automatically to 
avoid network loops and other problems. To avoid configuration problems, observe these guidelines and 
restrictions: 

Every port added to a port channel must be configured identically. No individual differences in 
configuration are allowed. 

Bundled ports can be configured on different line cards in a chassis.

Maximum Transmission Unit (MTU) must be configured only on port channel interfaces and this 
MTU is propagated to the bundled ports. 

Quality of Service (QoS) and Committed Access Rate (CAR) are applied at the port level. Access 
control lists (ACLs) are applied on port channels. 

MAC configuration is only allowed on port channels.

MPLS IP should be enabled on bundled ports using the mpls ip command.

You should apply Unicast Reverse Path Forwarding (uRPF) on the port channel interface using the 
ip verify unicast reverse-path command in interface configuration mode. 

The Cisco Discovery Protocol (CDP) should be enabled on the port channel interface using the cdp 
enable command in interface configuration mode. 

Enable all LAN ports in a port channel. If you shut down a LAN port in a port channel, it is treated 
as a link failure and its traffic is transferred to one of the remaining ports in the port channel. 

To create a port channel interface, use the interface port-channel command in global configuration 
command. 

When a Gigabit Ethernet interface has an IP address assigned, you must disable that IP address 
before adding the interface to the port channel. To disable an existing IP address, use the no ip 
address command in interface configuration mode.

The hold queue in command is only valid on port channel interfaces. The hold queue out command 
is only valid on bundled ports. 

This section includes these procedures: