Originally Posted By: DWallach
... I second the comment that, should you run a wire, it's really straightforward to add a new connector to it. The tools are designed to be idiot-proof, since electricians are often idiots. This means you may need to test that you terminated the wire correctly. At worst, I've needed 3 attempts to get a wire properly terminated.

...

. I don't know if it's feasible, but you could also investigate wireline networking. If the two apartments are on separate power meters, this would seem less likely to work, but it's certainly worth a shot.
Crimping an 8-pin UTP connector is generally a fiddly business, especially the first few times.

I will mention that it matters whether the individual thin wire conductors in the cable are flexible stranded wire or the stiffer 'solid conductor' type. The clear plugs that crimp on have different shapes to the tiny metal internal prongs. Using a 'stranded' connector on solid wire, or a 'solid' connector on stranded wire, will often result in a non-functioning connection, or even worse, a connection that becomes intermittent and troublesome over time.

Also be aware that one should not intermix CAT6 cables and crimp ends with CAT5e stuff. A pre-made CAT6 cable should work nicely with everything, but when hand crimping connectors the connector and cable must be of the same grade, CAT6 or CAT5(e).

Typically the cable that is sold on spools for running through walls and such is solid core wire while the pre-assembled Ethernet cables with connectors on both ends, aka patch cables, tend to use stranded wire for flexibility.

In this situation I would suggest using a factory assembled Ethernet cable with both ends in place, from a reputable source. Do not remove the end, make the hole big enough to fit the cable through without damage.

Look for either CAT5e or CAT6 rated cable. I consider CAT5 (without the e suffix) to be deprecated and not worth using as proper CAT5e cable is generally not more expensive.

Among low priced network cables it is not unusual for the ink printing on the cable jacket to over state the actual caliber of the cable product inside. There is almost no enforcement of technical standards regarding bulk manufactured cabling from low cost 'offshore' producers. Not just for Ethernet, of course, as we have seen with USB-C, HDMI, etc.

My own experiences with power line networking is that in almost every case I ended up removing the power line gear. Either it did not work consistently in the necessary locations, or it became troublesome later on. Often the problem causes were unclear ('electrical noise' from 'something' is often the prime suspect) or the power line devices themselves just became flakey.