Recently moved into a late 2000s home.
There’s some Cat 5e cabling throughout the house that’s only being used for telephone outlets. I can see not all the twisted pairs are being used.
There’s also a mess of cables next to the electric panel. How do I make sense of this and repurpose the Cat 5e for Ethernet?
If you want to also use the wiring for telephones then it gets a bit more complicated. That's because in ye olden times only two pairs were used for Ethernet so it was trivially easy to use one or two pairs for phone and the other two pairs for Ethernet. That is a bit different now. Basically, Gigabit Ethernet needs all 4 pairs. 100 Megabit can run on only two pairs, but that will limit your speed significantly, though whether it will limit it in a way that actually matters will depend on how you use your network.
There are a few pieces to making this work:
The first thing you need is a patch panel such as this Trendnet from Amazon:
You wire up each cable to the back of the panel. You use short patch cables like these from Amazon:
to connect from the patch panel to your router or switch. You can make your own cables, but for short lengths (at least up to 25') I find that it is not worth the hassle.
You install your router and/or switch (if you need more details on what those are, ask another question) somewhere on this wall.
At the other end - i.e., each jack in a room - you need to see what type of jacks you have. If they are Cat 5e 8-wire jacks then you just need to make sure they are connected properly to all 4 pairs. If they are something else (which is often the case for standard phone wiring, typically a 4-pin jack) then you need to replace the jacks.
For connecting to the jacks and the patch panel, you use a punch tool like this one from Amazon:
And finally, you should get a tester. There are a wide variety available. Really fancy models can detect line break distance and determine signal quality, etc. But most of the time you just need to know if the wires are connected identically on each end. A basic tester such as this one from Amazon:
will do the job.
One important thing to watch out for: Daisy-chained cables. Regular phone wiring, but not most "phone systems" and definitely not Ethernet, can chain from one jack to the next. With Ethernet, each jack has to have its own "home run" back to the patch panel/router/switch/etc.
You appear to have 3 or 4 Cat5e cables. If you have 3 or 4 phone jacks, you might be in luck, and all you need to do is terminate the cables onto Cat5e (or Cat6, if there's no upcharge on the jack price) jacks, and add a switch where they come together.
Jacks are available in several common formats - one variety needs a special tool to "punch down" the wires to the jack (sometimes a package of jacks includes a cheap plastic version of that tool) or there are "toolless" jacks available, sometimes for pretty much the same cost, which avoid the need to buy a tool just to do 8 or 12 jacks, one time, in your home. This is an example of a tooless jack - wires are inserted, then the lever is flipped down to connect them.
Image source. No endorsement (but I have done business with the company.)
Avoid the common mistake of crimping plugs onto wall cables. Jacks are far more reliable - use a patch cord to connect the jack to a device.
If you have more phone jacks than you have cables, the wiring is probably daisy-chained, which works for phone wiring but not for ethernet, unless you add a three-port (or more) switch at every point where a cable comes into one jack and goes on to another jack. Unsurprisingly, such switches, sometimes with built-in wifi access point as well, are available sized to mount to a standard junction box, and most are POE powered, so a single POE switch at the main junction point would deal with powering them.
Cat5e is fully qualified for gigabit ethernet up to 100 meters (which covers most houses....)
Supplemental answer, too long to add as a comment.
If your internet broadband service is less than 100mbps, you have no need of Gigabit between your router and any device requiring broadband access. So you can quite happily split a pre-installed cable between phone and 100Mbit Ethernet, the old-school way. It won't be a bottleneck.
If you want to run a household server or anything else that does need Gigabit, you install a Gigabit switch somewhere convenient, connected to the router at 100Mbit, and to household clients at Gigabit speeds. (You might also install a fast wireless access point connected to it, or use a wireless access point that also provides sufficient gigabit wired ports. Four is often plenty).
In my house I have a variant on this. I find Powerline networking works pretty well, so the router just connects to a Powerline networking "plug" and my home office picks up the network on another "plug". I didn't have pre-installed Cat5 and this solution meant I didn't need to install it. Wireless through foot-thick ironstone walls is hopeless! However, there's no way to find out about PowerLine networking other than buy (or borrow) and try. Your mains wiring is a completely unknown quantity.
How do I make sense of this and repurpose the Cat 5e for Ethernet?
trace every wire, label each, reroute to a different location away from the panel to tidy up; watch youtube how to punch rj-45 and rj-11 jacks, do patch panels, and do phone terminal blocks.
cat5e will only get you 1gbps speeds, given the hardware today and current trends unless you have a cable fetish or a radio signal phobia... wifi5 mesh routers which are now quite economical will have faster speeds than 1gbps on cat5e, up to around 3gbps. And then wifi-6 good up to ~9gbps, and new wifi-7 touted a theoretical 40gbps but real world from what I read is ~6gbps.
