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We just moved into our new house and found out that there are cat5e ports all over the house. I plugged in our router to the port and my pc into another but it doesn’t work. I found them all in a room downstairs and am wondering if they’re wired correctly. Two of them were just cut and disconnected from the rest so I connected them in the same way the others were but still nothing. They’re only connected by the blue wires and the blue and white wires which idk if that’s right or wrong. If you could help me out to get this working that would be great.

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    I don't know that I've ever seen old school CAT3/POTS wire terminated in wire nuts like that. That's... impressive...
    – FreeMan
    Commented Feb 25, 2022 at 0:33
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    That's a 4-pointed "star" configuration. We can't tell what's been done elsewhere, but "daisy chain" is where you have a jack with one cable coming in and another cable going out. Assuming that one of these cables probably leads outside to the NID, you can get from this point to whatever the first jack on each cable is via re-terminating correctly and using a switch, so probably 3 jacks. If those jacks have other cables leading out from them, they would have to be removed, as those would be the "daisy-chain" connections we can't support (unless via a 3-port switch at the jack location.)
    – Ecnerwal
    Commented Feb 25, 2022 at 13:31
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    Newly built home, or newly-purchased existing home?
    – RonJohn
    Commented Feb 25, 2022 at 23:50
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    When you write "cat5e", do you mean "Something that looks like I could plug my computer in to it", or did you actually check the cables?
    – pipe
    Commented Feb 26, 2022 at 11:20
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    The ports may be 5e, but with wiring like that the cabling definitely no longer is.
    – Mast
    Commented Feb 26, 2022 at 16:22

4 Answers 4

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They are wired correctly for telephone (POTS, Plain Old Telephone Service, single pair) per your description.

To use them for ethernet would require re-terminating, and depending how they are run, possibly some won't work (things that work fine for POTS don't for ethernet, such as multiple connection points on one cable.) You might get lucky if they are in fact all single runs from the central location, in which case a patch panel and switch there would allow distribution to all the other locations.

You should identify what cable leads outside where the telephone company Network Interface Device is, and NOT attempt to connect ethernet to that one.

10/100 Mb ethernet needs two pairs, gigabit ethernet needs all 4 pairs, and you can't just wirenut them together...

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    Yeah. Buy a crimper, a bunch of RJ45 jacks (I'd suggest a box of 50 - they'll be cheaper per, plus when you're learning you'll get more than a few wrong), and a cable tester to make sure they're crimped correctly. The whole batch can probably be had for under $100.
    – FreeMan
    Commented Feb 25, 2022 at 0:34
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    Nope. Done right, you punchdown into jacks (them are the female bits), and use factory-made patch cables anywhere you require a plug (the male bits that crimp.) They can be had cheaper than the parts to make 'em. Crimping plugs onto solid wall cable is not generally reliable and not recommended as a result. Plus, an inexpensive punchdown tool is less expensive than a decent crimper. And punchdowns can be re-done if you mess up, rather than cut-off-and-throw-away. You also don't need a cable tester if you have two things that will indicate that they are connecting at gigabit speed, or not.
    – Ecnerwal
    Commented Feb 25, 2022 at 0:37
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    I don't think there's any post here that will transform complete ignorance of how ethernet wiring is correctly accomplished to knowledge of how to do it. That's a very large amount of learning, it's entirely possible to do it (ignorance is curable) but it comes closer to being a book than something in the scope of this site. We have a number of similar questions, but none of the answers I've glanced at suit that purpose. Most of the other websites I've looked at in hopes of finding you one are either attempting to upsell products or full of misinformation (or both.)
    – Ecnerwal
    Commented Feb 25, 2022 at 2:47
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    But someone else may have a site suggestion. I'm a poor source for a website for starting from scratch, as I started from scratch before there was a world-wide web (and I can connect 10Base5 cables with vampire taps - which is an utterly useless skill for decades now.) en.wikipedia.org/wiki/10BASE5
    – Ecnerwal
    Commented Feb 25, 2022 at 2:51
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    A cable tester would be a great investment in almost any case - you'll need to trace the cables to work out where they go and if you're reterminating them, to at least do a minimal functional check Commented Feb 25, 2022 at 13:03
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Yikes!POTS wiring is usually done in a daisy topology (from one jack to the next), no way will that work with IP protocol/Ethernet/internet, it has to be wired in a star topology (each jack having a home run to the router or modem). if wired as POTS, you have a lot of work to do...also, if the structure of the of the home makes it difficult to run home runs, you might consider WIFI for some locations. If devices you might have don't have WIFI capability, you can connect another router in bridge mode, then it appears like a hard wired connection to the device.

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  • Or put in switches wherever the POTS splits into 2 or more wires. May be more expensive, but easier. Commented Feb 27, 2022 at 19:44
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For 10/100Mbps you need 2 pairs, for gigabit you need all 4 pairs.

Due to high frequency signals involved, cables need to be terminated properly so their impedance stays constant through the line. Using wire nuts like that will create an impedance discontinuity which will destroy the signal integrity (ie, Ethernet won't work). So you will have to get rid of all the wire nuts anyway.

So, first you need to map how the wires are connected in the house. If this was used for phones, you could have outlets connected in daisy chain, and that won't work. Ethernet needs a star topology, with a cable from each outlet to the switch, and outlets can't be daisy chained.

You can open all the outlets. If there's only one cable inside and no sign of daisy chaining, you're on the right track. You should also check all the 8 wires are connected to each socket, because if the installation was wired for phone use only, maybe they didn't bother. Also time to check the jacks are Cat5 with 8 contacts and not just plain phone jacks. Google "RJ45 wiring" for which color goes where.

Once you've figured that out, you can buy an Ethernet patch panel and install it where all the cables come out (in the picture in the question). Then you can connect all the cables and wire the panel to your switch/router with short cheap patch cables.

Connecting an Ethernet device will just tell you "doesn't work" or "100 Mbps only" (which means the 2 center pairs are correct) or "gigabit" (which means all 4 pairs are correct). You can also get an Ethernet cable tester, this will usually give more detailed information about which wires are wired wrong.

If there are more wire nuts inside the walls, though, it won't work.

It's not difficult to do, but if you've never done it before, you should check for documentation and tutorials online.

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    Technically splicing with wirenuts will work (assuming star topology), but the error rate will be so high that bandwidth will be very low. [It is worth noting that "technically correct" is the worst kind of correctness, of course]
    – Ed Griebel
    Commented Feb 26, 2022 at 15:56
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Here's a fun fact: Ethernet jacks (RJ45) are designed to be backwards compatible with their Phone (RJ11) counterparts. If you look at any Ethernet wiring diagram, pins 4 and 5 are the blue wires in all forms of Ethernet, which is what they are using in your wires here.

If I were you, here's what I would do: change out your RJ11 for RJ45 jacks on both ends (wall plates and your basement). For the end in your basement, you can buy what's called a patch (or punch) panel. You'll want a punch-down tool for this project. Also, you'll want to note which cable goes where, as you connect them (a wire tracing tool like a tone generator can be helpful for this). The other end will entail installing keystones (which are the same as your punch panel) and wall plates for the keystones. Once you have your wires terminated as RJ45, you can then plug the patch panel to a switch and connect the switch to your Internet and have a fully functional home network.

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    While there are no pictures of that end, I assume they actually have RJ-45s as wall jacks, since they plugged in the router and PC. Likely even "Cat5e" RJ45s, as I read the question. Likely with only the blue pair connected, of course.
    – Ecnerwal
    Commented Feb 25, 2022 at 15:42
  • Do phones do that? I thought phones use RJ11s, and they look like smaller RJ45s Also I suspect simply installing keystones on either end, then plugging in one and and testing would be the lazy solution, especially since keystones arn't crimped Commented Feb 26, 2022 at 1:08
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    They do. You can wire the blue wires up and stick an RJ11 plug into a RJ45 jack and it will work.
    – Machavity
    Commented Feb 26, 2022 at 1:17

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