networking – Separate connections over 1 network cable

Consider the following network setup

                         ┌───────────────┐                                
┌────────────┐           │               │               ┌───────────────┐
│            │           │  2 Port RJ45  │               │               │
│ ISP / DHCP │──────────▶│  Socket Roof  │──────────────▶│ Unifi AP Roof │
│            │           │               │        B      │               │
└────────────┘     A     └───────────────┘               └───────────────┘
                                │  ▲                                      
                                │  │ B                                    
                                │  │                                      
                                │  │                                      
                             CAT6 Split                                   
                                into                                      
                              2x100MBit                                   
                                │  │                                      
                                │  │                                      
                              A │  │                                      
                                │  │                                      
                                ▼  │                                      
                         ┌───────────────┐                                
                         │  2 Port RJ45  │                                
                         │ Socket Ground │     B                          
                      ┌──│     Floor     │◀───────────────────────┐       
                      │  │               │                        │       
                      │  └───────────────┘                        │       
                      │                                           │       
                      │                                           │       
                   A  │                                           │       
                      │                                           │       
                      │      ┌────────┐               ┌────────┐  │       
                      │      │ Unifi  │        B      │ Unifi  │  │       
                      └─────▶│  USG   │──────────────▶│  PoE   │──┘       
                       WAN/1 │        │ LAN/1         │ Switch │          
                             └────────┘               └────────┘                  

Now the issue is there is only one cable run from the roof to the network rack on the ground floor. To get 2 connections out of this I have split the CAT6 cable up into 2×100 MBit using 4 wires each.

So the network is as follows:

  • The ISP comes in on the roof via a standard RJ45 (radio relay)
  • The cable is then connected to a 2 port socket (port A) I wired up to split the cable into
    2x100MBit
  • On the ground floor the cable from A is connected to the USGs WAN/1 port.
  • From the USG LAN/1 port it goes to a PoE switch that connects the rest of the local lan
  • One PoE port from that switch goes back to the 2 Port socket on port B
  • Port B of the socket on the roof is then connected to the AP

Now I can’t say I really like this setup very much. The reasons this is set up this way is

  1. I am a network noob and probably don’t know better
  2. I wanted to power the roof AP via POE without an additional injector (not that important)
  3. I wanted to isolate the ISPs DHCP by splitting it into 2 physical connections and using the USGs DHCP instead (important)

So the question is:

Can I achieve those goals without splitting the cable up into 2x100MBit, e.g. using a USW Flex Mini switch?