You can configure a LAG by specifying the link number as a physical device and then associating a set of ports with the link. All the ports must have the same speed and be in full-duplex mode. JUNOS software for Gigabit Ethernet uPIM switches assigns a unique ID and port priority to each port.
The ID and priority are not configurable. When configuring a LAG, consider the following guidelines:
A typical deployment for a LAG would be to aggregate trunk links between an access switch and a distribution switch or customer edge (CE) device. LAGs are not supported on virtual chassis port links. LAGs can only be used for a point-to-point connection. Atleast one end of the LAG should be configured as Active