Milan Technology MIL-SM2401M-STK - Manual (Page 167)

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7-4-5-3. State Activity
Active (selected): The active port automatically sends LACP protocol packets.
Passive (not selected): The passive port does not automatically send LACP
protocol packets, but responds only if it receives LACP protocol packets from
the other device.
A link having either two active LACP ports or one active port can perform
dynamic LACP trunking. A link that has two passive LACP ports will not perform
dynamic LACP trunking because both ports are waiting for an LACP protocol
packet from the opposite device.
If the port has active LACP’s, and you select the trunking port, the active status will be
created automatically.