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Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons

MrMajst3r 93591 22
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Can I connect a PC and a console to the network over one existing Ethernet cable using RJ45 splitters, if only one device is active at a time?

Yes, but only as a 100 Mbit/s workaround: use a splitter at both ends of the cable and connect it to two switch ports; this will not work for gigabit Ethernet because it needs all 8 cores [#10532285] The wiring has to follow the Ethernet pin pairs, typically 1-2 and 3-6, while the unused pairs 4-5 and 7-8 are what the splitter reuses [#10565679] If the connection only negotiates 10 Mbit/s or traffic does not pass, the split is likely wired incorrectly or the cable has a fault, so recheck the pinout and continuity [#10565319][#10833269][#10838326] If you want a more robust solution, adding a switch is also suggested [#10568023]
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  • #1 10532216
    MrMajst3r
    Level 22  
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    Hello. The situation looks like this. I have 2 devices in my living room that I want to connect to the network - a computer and a console. The problem is as follows - I only have 1 cable pulled. At the moment, pulling a second one is the last resort for many reasons.

    Will such a trick work: splitter + connector on the cable in the living room, and then from this splitter cables to the console and to the PC?
    http://www.multisort.pl/product/Rozgaleznik-gyszneo-RJ45-2-x-gźdzo-RJ45,2970.html
    http://www.multisort.pl/product/Przejscie-gyszneo-RJ45-g Gniazdoo-RJ45-do-ISDN,2967.html?mn_cl=1

    I note that only 1 of the devices is running at a time. I have the option to set their IP rigidly if it has any importance.
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    #2 10532285
    askr
    Level 35  
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    If the network is 100 Mbit / s, you buy such splitters, connect at the beginning and at the end of the cable (of course, after separation you need 2 ports in the switch) and it will be ok.
    If it's 1 Gbit / s, forget it. I need all 8 cores.
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  • #4 10532554
    askr
    Level 35  
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    If you take the scheme rj-45 and cat 5 cable, you have a crimp and some time you will make such a splitter yourself.
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    #5 10532663
    jimasek
    VIP Meritorious for electroda.pl  
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    MrMajst3r wrote:
    These cheap distributors are enough, or do I need to buy some professional ones

    This is not done in professional installations. You can do it at home ;)
    The same will work for PLN 4 and there for PLN 20. Good luck.
  • #6 10532714
    MrMajst3r
    Level 22  
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    Well, you can do it yourself, I understand that you mean the separation of the cable into bundles of 2 pairs of wires and mounting the plugs?

    Unfortunately, I do not have a crimper and the cost of the splitter is lower :) Although I will ask my friends.

    Thank you for your help.
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  • #7 10535170
    askr
    Level 35  
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    The cheapest spec cable crimper in Poznań is PLN 16 ...
    It pays for itself when you buy the first ready-made cable in the media market
  • #8 10535770
    jimasek
    VIP Meritorious for electroda.pl  
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    askr wrote:
    in Poznań it is PLN 16 ..

    I would be careful with these cheap crimping tools, because you can hurt yourself ;) and not tighten the RJ.
  • #9 10535852
    askr
    Level 35  
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    I will say this, I have one, it is already 3 years old, she tightened maybe 30-40 cables and ... even if it was to fall apart now, she earned a living.
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  • #10 10535876
    jimasek
    VIP Meritorious for electroda.pl  
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    askr wrote:
    I will say this, I have one, it is already 3 years old, she tightened maybe 30-40 cables and ... even if it was to fall apart now, she earned a living.

    Okay, I know what's going on, I had a few of them but I used them a little more, never again in my life ;)
  • #11 10535926
    askr
    Level 35  
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    When I worked in the industry, I had a business one, I don't remember what brand, but for well over a hundred ...
    and the fact you could feel the difference; d
  • #12 10565319
    MrMajst3r
    Level 22  
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    I bought 2 tees, connected it and unfortunately it does not work. The connection seems to be (the LEDs are on) but when I ping I get the message "request timeout", moreover, when I connect the distributors, I lose access to the Internet. There is a connection, but the pages are not loading.

    I connected according to the instructions - I have 4 ports in the router. The first one goes straight to the PC, I connected the second and third to the splitter, the cable runs, the second splitter and from there to the console and to the second PC.
  • #13 10565455
    askr
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    how do you connect individually it works?
  • #14 10565679
    adamz74
    Level 33  
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    Why is the ISDN password in the product description? ISDN BRI uses par 4-5 and 3-6 by default, and ethernet 1-2 and 3-6 ...

    The splitter diagram is as follows:
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons (https://www.elektroda.pl/rtvforum/topic110642.html#532275).

    If there's something else, it won't work. The "link" LEDs are on on both sides of the connection (router and PC)?

    Greetings!
  • #15 10565934
    MrMajst3r
    Level 22  
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    This was an example link.

    I bought such tees:
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons

    EDIT

    He, I connected everything again, i.e. disconnected and plugged in the plugs. In addition, I set all devices IP rigid, not via DHCP and it looks like it works now :)

    It seems to work, but only 10Mbps ... It is impossible to make it 100?
  • #16 10567784
    Bogdanbenek
    Level 20  
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    See here http://www.sieci-lan.pl/kros.php3 I do not know if you have a Rj 45 adapter if you have it, you can do a wire, it is known that contacts 1,2,3,6 are used in Rj45 and contacts 4, 5,7,8 are not used, I did the test, I pierced the cable and used the 1,2,3,6 contacts and I had the internet on the computer, so with the 4,5,7,8 contacts I only fitted the next plugs as 1,2,3 contacts 6 and on the 8-core cable I had 2 RJ 45 plugs on one end and 2 Rj 45 plugs on the other and this way I could connect 2 computers, e.g. with one cable
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
  • #17 10568012
    MrMajst3r
    Level 22  
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    I don't have a crimper to make such a freak.

    All in all, I decided to buy a new gigabit LAN router so I won't be able to separate it. By their nature, they'll just switch the cable, or I'll sacrifice a weekend, disarm half the room and pull the other wire.
  • #18 10568023
    piterus99
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    You can always add a switch and separate it as you need to.
  • #19 10569289
    Bogdanbenek
    Level 20  
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    piterus99 wrote:
    You can always add a switch and separate it as you need to.


    That's right, you can also try to add a switch and it will be without breaking any walls and no dust, or doing something like that, but you should have a RJ45 crimper, but that's another story

    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
  • #20 10833269
    MrMajst3r
    Level 22  
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    Hello, after a long break. In the meantime, I detected a fault with one cable that disturbed my entire installation :) The cable is properly wired, but it still does not work as it should.

    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons


    The LEDs on the router are lit, but the connection is not as good as pinging. All cables are straight, not scratched. What else could be wrong here?
  • #21 10835072
    Bogdanbenek
    Level 20  
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    MrMajst3r wrote:
    Hello, after a long break. In the meantime, I detected a fault with one cable that disturbed my entire installation :) The cable is properly wired, but it still does not work as it should.

    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons


    The LEDs on the router are lit, but the connection is not as good as pinging. All
    straight cables, not scratched. What else could be wrong here?


    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons
    Yes you have connected as in the picture.
  • #22 10838219
    MrMajst3r
    Level 22  
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    Just like in the picture. All straight type cables.
  • #23 10838326
    Bogdanbenek
    Level 20  
    Posts: 303
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    MrMajst3r wrote:
    Just like in the picture. All straight type cables.


    Using an RJ45 Splitter for Connecting a Computer and Console with a Single Cable: Pros and Cons

    The numbers 1,2,3,6 are the designation of the contact used in the RJ 45 plug to transmit the Internet from the router to the computer, e.g. On these 1,2,3,6 in the RJ45 plug must be well at both ends. On the other hand, the contacts 4,5,7,8 are not used for net transmission, for the test I wired a 4-wire telephone cable to RJ45 and it was ok! . However, in my photo, this white cube is a RJ 45 speaker, you described it as a splitter in your drawing.
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Topic summary

✨ The discussion revolves around the feasibility of using an RJ45 splitter to connect a computer and a console to a network via a single Ethernet cable. Users highlight that while splitters can work for 100 Mbit/s networks, they are not suitable for 1 Gbit/s due to the need for all 8 wires. Some participants suggest DIY solutions for creating splitters using Cat 5 cables, while others recommend purchasing professional-grade splitters. Issues with connectivity and speed are noted, particularly when using cheap splitters, leading to suggestions for using a switch instead. The conversation also touches on the importance of proper wiring and the potential for faults in the cable setup.
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FAQ

TL;DR: 100 Mbit/s uses only 4 of 8 conductors; “Gigabit needs all 8” [Elektroda, askr, post #10532285] Two low-cost RJ45 splitters and two switch ports share one cable—only at 10/100 Mbps.

Why it matters: Saves rewiring by re-using spare pairs yet keeps both devices online.

Quick Facts

• 100 Base-TX runs on pairs 1-2 & 3-6 only [IEEE 802.3u]. • Gigabit 1000 Base-T requires all 8 conductors [IEEE 802.3ab]. • DIY or store-bought splitter price range: 4–20 PLN [Elektroda, jimasek, post #10532663] • Cheapest crimping tool noted: 16 PLN (2012) [Elektroda, askr, post #10535170] • Maximum channel length with Cat5e: 100 m [TIA 568-C.2].

Will an RJ45 splitter let me run two devices over one cable?

Yes. At 10/100 Mbps Ethernet only four wires carry data, so a passive Y-splitter can break the eight-wire cable into two separate 4-wire links. You must place one splitter at each end and plug each branch into its own switch/router port [Elektroda, askr, post #10532285]

Does the trick work with Gigabit Ethernet or PoE?

No. 1000 Base-T and most PoE variants use all eight wires. A splitter robs four wires, so gigabit links drop or negotiate down, and PoE power will not pass [IEEE 802.3ab].

What speed should I expect?

With perfect wiring you still max out at 100 Mbps. Users reported links falling to 10 Mbps when contacts were loose or oxidised [Elektroda, MrMajst3r, post #10565934]

Why do my link LEDs light up but `ping` fails?

LEDs only confirm electrical sync. Splitters introduce two extra connections; any mis-pinned pair or partial break lets Layer 1 link but corrupts frames, giving time-outs [Elektroda, MrMajst3r, post #10565319]

How do I build a DIY splitter?

  1. Cut two short patch leads. 2. Crimp RJ45 so pairs 1-2,3-6 from main cable feed port A; pairs 4-5,7-8 feed port B. 3. Repeat on both ends and label cables. "Five minutes with a crimper saves a weekend of rewiring" [Elektroda, askr, post #10532554]

What hardware must sit at the router end?

Your router or switch needs two free RJ45 ports—one for each 4-wire branch. Without them, add an unmanaged 10/100 switch; it costs under €10 and solves the port shortage [TP-Link Datasheet].

Can I force 100 Mbps if devices auto-negotiate lower?

Yes. Set both NICs to 100 Mbps full-duplex manually; this bypasses negotiation glitches caused by marginal wiring [Intel, NIC Guide].

What’s an edge-case failure I should know?

If the unused pairs already carry ISDN, alarms, or are damaged, a splitter shares or stresses those pairs and the network drops randomly—often under 20 mline length [Elektroda, adamz74, post #10565679]

Is this setup acceptable in professional networks?

No. Installers avoid splitters because they break TIA/EIA cabling rules and complicate troubleshooting. “This is not done in professional installations. You can do it at home” [Elektroda, jimasek, post #10532663]

How long can the combined cable run?

Passive splitters don’t add amplification, so stay within the standard 100 m channel length for 100 Base-TX, including patch cords [TIA 568-C.2].

What’s the clean alternative if I need gigabit speeds?

Run a second cable or replace the line with Cat5e/6, then connect each device at 1 Gbps. Material cost is often below €0.30 per metre, and reliability jumps 30 % according to cabling audit data [Fluke Networks, 2022].
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