While it would make more sense to use a purpose made RJ45 Data/Data splitter you can make do with a Phone/Data Splitter and a custom made CAT-5e cable.
The Phone/Data splitter passes 1, 2, 3, and 6 straight through, so the first part of the Data/Data splitter is easy (naturally).
The phone part maps 4, 5, 7, and 8 to 4, 5, 3, and 6 respectively.
I made a custom cable to map the phone pins back to the data pins where:
- Pin 1 (orange white) goes to Pin 3
- Pin 2 (orange) goes to Pin 6
- Pin 3 (green white) goes to Pin 5
- Pin 4 (blue) goes to Pin 2
- Pin 5 (blue white) goes to Pin 1
- Pin 6 (green) goes to Pin 4
- Pin 7 (brown white) goes to Pin 7
- Pin 8 (brown) goes to Pin 8
Expressed as pins:
- Pin 1 (blue white)
- Pin 2 (blue)
- Pin 3 (orange white)
- Pin 4 (green)
- Pin 5 (green white)
- Pin 6 (orange)
- Pin 7 (brown white)
- Pin 8 (brown)
