Correct Order of L2 Etherchannel Configuration

Entire networks can go down if the etherchannel is not configured correctly or in correct order.

1. Go to the physical member interfaces with blank configuration  & assign the channel group to the physical member interfaces. Do this on both switches..

SW1(config )#int range e0/0-1

SW1(config-if-range)#channel-group 1 mode active

2. Go to the portchannel interface and apply the configuration after the portchannel is operational, you must do all other configuration (trunk/access, allowing vlans etc) only inside the portchannel interface.

SW1(config )#int po1
SW1(config-if-range)#switchport trunk encapsulation dot1q
SW1(config-if-range)#switchport mode dynamic desirable
SW1(config-if-range)#switchport trunk allowed vlan 10,20

If everything went ok, following outputs will be present.

If it says (SU) it's an L2 etherchannel and it is working. (P) after the member interfaces indicate they are correctly bundled in..

Here the protocol I used is LACP. So the other end must be configured as channel-group mode active or passive..

Here are the 2 protocols to negotiate etherchannels..

1. LACP (active & passive)
2. PAGP (desirable & auto)

Active and desirable modes start negotiation while passive and auto modes listen only..

You can create a channel even without a negotiating protocol by issuing the both ends to be "on"..
Best practice is to use a protocol because "on" can lead to many catastrophes. Even the total network can go down because of a single misconfiguration.

Additional load balancing can be done in global configuration mode.
SW1(config)#port-channel load-balance src-ip