This article describes the issue of the DAC (Direct Attach Cable) interface not coming up on QFX-series switches that use the 42-47 and 0-5 Fiber Channel ports.
On QFX-series switches, the Direct Attach Cable (DAC) interface does not come up, when a DAC is attached to the 0-5 or 42-47 interfaces; regardless of whether the interfaces are in the 10-Gigabit Ethernet mode or native fiber channel.
This issue has been resolved from 11.3R5 or later.