While easy to work out via the ‘?’ in the Switch’s CLI. A quick table to remember the required modes to Establish Etherchannel between two switches.
| Switch 1 | Switch 2 | EtherChannel Up? | |
| No Negotiation | On | On | Yes |
| LACP Combination 1 | Active (Initiate LACP) | Passive (Listen for LACP only) | Yes |
| LACP Combination 2 | Active (Initiate LACP) | Active (Initiate LACP) | Yes |
| LACP Combination 3 | Passive (Listen for LACP only) | Passive (Listen for LACP only) | No |
| PAgP Combination 1 | Desirable (Initiate PAgP) | Auto (Listen for PAgP only) | Yes |
| PAgP Combination 2 | Desirable (Initiate PAgP) | Desirable (Initiate PAgP) | Yes |
| PAgP Combination 3 | Auto (Listen for PAgP only) | Auto (Listen for PAgP only) | No |
For more information on configuration and configuration modes vist the configuration guide on the doccd for the 3560 here.
EtherChannel On Mode
EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port to join an EtherChannel without negotiations. The on mode can be useful if the remote device does not support PAgP or LACP. In the on mode, a usable EtherChannel exists only when the switches at both ends of the link are configured in the on mode.
Ports that are configured in the on mode in the same channel group must have compatible port characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they are configured in the on mode.
Port Aggregation Protocol
The Port Aggregation Protocol (PAgP) is a Cisco-proprietary protocol that can be run only on Cisco switches and on those switches licensed by vendors to support PAgP. PAgP facilitates the automatic creation of EtherChannels by exchanging PAgP packets between Ethernet ports.
By using PAgP, the switch learns the identity of partners capable of supporting PAgP and the capabilities of each port. It then dynamically groups similarly configured ports into a single logical link (channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and port parameter constraints. For example, PAgP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, PAgP adds the group to the spanning tree as a single switch port.
Link Aggregation Control Protocol
The LACP is defined in IEEE 802.3ad and enables Cisco switches to manage Ethernet channels between switches that conform to the IEEE 802.3ad protocol. LACP facilitates the automatic creation of EtherChannels by exchanging LACP packets between Ethernet ports.
By using LACP, the switch learns the identity of partners capable of supporting LACP and the capabilities of each port. It then dynamically groups similarly configured ports into a single logical link (channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, LACP adds the group to the spanning tree as a single switch port.
