Sorry for the vague title, but I can't really describe it more succinctly.
A friend of mine (who is also an electrician) put in some data ports throughout my house - one in the lounge, one in the theatre room, one in my office, and one in my shed. Here's a diagram:
I can plug a device into any outlet and get a connection, apart from the outlet in the shed (marked in red). However, if I bypass the central switch (only for the line that runs to the shed, highlighted below) then I do get a connection in the shed:
Here are a list of things we've tried to rectify this:
- Completely replacing the line running to the shed, just in case it was in some way at fault
- Ensuring the line to the shed is pulled away from nearby electrical cabling, just in case interference was to blame
- Enclosing the line to the shed in conduit to further minimize any potential electrical interference
- Replacing the lead between the central switch and the router
- Replacing the lead from the 4 gang wall outlet to the switch
- Detaching everything else from the switch and only attaching the line to the shed
- Swapping to a different port on the switch (just in case one port was faulty)
- Swapping the two switches around
None of these things has worked and we're completely baffled. Can anyone offer any explanation and resolution to this issue?
EDIT (after several comments):
Some extra info:
- The electrician did test the wiring using a testing tool, and it reports a positive result
- It's Cat6 cabling
- I used the same device (a laptop running Linux Mint 17) to test every port
- I just printed out my floor plan and measured distances from the switch to both the shed and lounge. The straight-line distance to shed is shorter, but the path is more circuitous, so I think the cabling length would be longer by around 4 to 5 metres, but we're still only talking 25-30 metres long
- The shortcut cable I used was different because I needed a longer one for the shortcut. However, I did try multiple cables in every position, so I don't think it's the cable. To be certain, I just used the shortcut cable between the switch and 4-gang outlet, and the connection in the shed still doesn't work

