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Can I have one 4-twisted-pair cable (cat5) and split them into 2 ethernet ports? I know ethernet only needs 4 wires so that wouldn't be the problem but will it interfer with eachother or would that be no issue?

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    You shouldn't actually open up the cable and just take some of the wires for one computer, and some of them for the other. splitters are available but your router/modem will need to have two available ports (one for each of the connected devices), so all it does is 'combine' the two cables into one for most of the way. I'd recommend getting a switch to do your splitting so it can retain your full speed and you're not doing some hacky solution.
    – Cas
    Dec 20, 2016 at 8:56
  • Sorry @cascer1 - I didn't mean to steal your comment. I actually posted my answer before I read your post.
    – Tetsujin
    Dec 20, 2016 at 9:03
  • @Tetsujin Don't worry about it :)
    – Cas
    Dec 20, 2016 at 9:03
  • "It will be used to connect multiple pc's to the same network" -- Then you're asking an XY question. All you need is an Ethernet switch.
    – sawdust
    Dec 20, 2016 at 19:58
  • So, this question is a duplicate of a duplicate?
    – isanae
    Dec 21, 2016 at 0:28

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Yes, it will work, though it will be limited to 100 Base-T speeds.

However...
For the price of two splitters & the extra cables you'd then need at each end, you could probably get a cheap ethernet switch & keep your 1000 Base-T speeds.

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    There's a reasonable chance it'll drop down to 10 Base-T speeds. Totally worth the ethernet switch IMO.
    – Journeyman Geek ♦
    Dec 20, 2016 at 10:33
  • Will the speed be degraded permanently or only while using both sockets?
    – Shimmy Weitzhandler
    Jul 3 at 11:35
  • As permanently as the ports are split. You'd have to set up two hardware ports, each with only 4 of the 8 wires. 1000BaseT needs all 8, 100BaseT can run on 4.
    – Tetsujin
    Jul 3 at 11:57
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You could use VLANs and give each "cable" a VLAN number, that way computers set to a particular VLAN will only see packets tagged with that VLAN number, using a standard (unmanaged) switch to split the cable into multiple ports.

You could also use a managed (business-grade) switch that could handle the VLANs by itself and assign each VLAN to a particular port, that way the computers don't need any configuration and it's a bit more secure as the machines don't receive the packets of the adjacent VLAN (where as in the first situation the packets still reach both machines, so if any are evil they could still listen into the adjacent VLAN's traffic).

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Yes, this will work fine if you use two proper fast Ethernet splitters, one on each end. Speed will be limited to 100Mbps -- gigabit Ethernet won't work as it uses all four pairs.

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You could also use a VLAN, depending on the reason behind needing two Ethernet connections.

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  • It will be used to connect multiple pc's to the same network. Not sure how a VLAN has to do with this?
    – Ravenix
    Dec 20, 2016 at 9:24
  • Maybe you should put that in the question to help out others trying to assist you.
    – AyeitzaMoleRat
    Dec 20, 2016 at 9:26

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