The information on this page supplements the official manuals.

What's FASLINK?

FASLINK: a proprietary Fractal Audio communications link between the Axe-Fx II and MFC-101, featuring bi-directional MIDI and power over a standard XLR microphone cable. Cable runs of hundreds of feet are possible. XLR cables are more flexible and robust than Ethernet cables.
FASLINK II: a proprietary Fractal Audio communications link between the Axe-Fx III and the FC foot controllers, featuring communications and phantom power over a standard XLR microphone cable.

Hardware support for FASLINK

FASLINK: The Axe-Fx II XL/XL+ and MFC-101 Mark III models have built-in FASLINK support. Older Axe-Fx II models (Mark I, Mark II) and MFC-101 models (Mark I, Mark II) require FASLINK adapters XA-1 and XA-2 to convert the wiring between XLR and Ethernet/Ethercon. These adapters are "active" (source). They can be bought directly from Fractal Audio's online shop.
FASLINK II: the Axe-Fx III and the FC -6 and FC-12 controllers support FASLINK II.

Axe-Fx III: (...)
Axe-Fx II: turn on FASLINK in the I/O menu.
MFC-101: select the correct port in the MFC settings. Do not connect a power supply to the MFC-101 when using FASLINK.

"The FASLINK port is protected against shorts." source