Answer
For Layer 3 traffic, the default components used to calculate the load balancing (hashing) algorithm for a link aggregation group (LAG) are the source address, destination address, and interface indexes. If you include the hash-key statement under the [edit forwarding-options hash-key] hierarchy level, the information in that level is used to compute the hash key for load balancing.
Junos OS supports a maximum of 128 link aggregation group bundles (LAG) bundles with 16 members each on MX Series routers.
For more information, click Layer 2 VPNs and VPLS Feature Guide.