EtherChannel - LACP System ID

When using Link Aggregation Control Protocol (LACP) to create an EtherChannel, each switch obtains an LACP system ID. This ID is composed of the LACP system priority and the MAC address of the switch.

To view the LACP system ID, use the following command:

SW2#show lacp sys-id
32768, 5254.0018.8000

The switch with the lowest LACP System ID is responsible for making decisions about which ports actively participate in EtherChannel. This switch is often referred to as the "master" switch, although this is not an official term.

To determine which device has the lowest system priority when you have access to only one device, you can use the show lacp neighbor command. This command provides information about the remote device's priority. For example:

SW2#show lacp neighbor
Flags:  S - Device is requesting Slow LACPDUs
        F - Device is requesting Fast LACPDUs
        A - Device is in Active mode       P - Device is in Passive mode

Channel group 1 neighbors

Partner's information:

                  LACP port                        Admin  Oper   Port    Port
Port      Flags   Priority  Dev ID          Age    key    Key    Number  State
Gi0/1     SA      32768     5254.0005.8000  23s    0x0    0x1    0x2     0x3D
Gi0/2     SA      32768     5254.0005.8000  17s    0x0    0x1    0x3     0x3D

If the system priorities are the same, the device with the lowest MAC address will be the decision-maker for establishing the aggregation.