Etherchannel L2 Free Error Loops

The Etherchannel is an aggregated set of several physical interface as a single logical interface. The purpose of Etherchannel is to provide greater capacity than a single avaibility physical interface. The creation of danger to avoid is forwarding loops, due to two interface or more connect to same device. The Spanning Tree Protocol (STP) should be avoid forwarding loops, but some condition for example channeling ports aren't consistent, intermittent physical layer can be reason of forwarding loops.

To avoid forwarding loops, this is best practices to config Etherchannel L2.

#### Shutdown all member interface, use interface range to easy config several interface

IOS-A(config-if)# interface range FastEthernet1/0-1
IOS-A(config-if-range)# shutdown

#### Switch interface to layer 2

IOS-A(config-if-range)# switchport

#### Define trunk encapsulation, dot1q or isl

IOS-A(config-if-range)# switchport trunk encapsulation dot1q

#### Enable mode trunk

IOS-A(config-if-range)# switchport mode trunk

#### Add vlan member to interface

IOS-A(config-if-range)# switchport trunk allowed vlan 11,13,15

#### Create port-channel interface and mode active, for other side is passive

IOS-A(config-if-range)# channel-group 1 mode active

#### Enable interface

IOS-A(config-if-range)# no shutdown


#### Verify

IOS-A# show ip interface brief

IOS-A# show etherchannel summary