I'm pretty sure that the Juniper QFX5100 and the Juniper ACX5048 are some box with different Junos and features allowed/disallowed...somehow. (lookup pictures on google and juniper.net... pretty sure identical box)
As I recall, the QFX5100 has more data-center-type things like virtual chass/mc-lag and less MPLS-edge-agg... As I recall (actually know from deploying 25 of them now), the ACX5048 has more MPLS-edge-agg and less data-center-type things like virtual chass/mc-lag -Aaron
