I’ll add for sake of completeness that there are some WiFi extenders which will not allow access between those computers on your network which are connected to your main router and those which are connected to your extender. So if you are using the extender for your WiFi, you might be able to access the larger internet, but not the printer that’s using your main router’s WiFi connection.
Mesh routers should put everything into the same network, and thus will allow that printer connection.
I have an old house, brick, and all the plaster is 1” thick. The ceilings are all wire mesh lath. This place is an internet killer. The router is in the basement and provides serviceable internet to most of the first floor and garbage to the second. Where my office is.
So while I had some walls open for some wiring, I ran an ethernet cable and installed one of these with a POE injector. It works great
ETA: I put it at the landing at the top of the stairs to the second floor, and it serves both floors well.
FYI, in the US, TP-Link is currently under a national security investigation and also a price-dumping antitrust investigation… not sure how much of that is political grandstanding and how much of a legitimate concern there is. (Edit: All the signatories of the national security letter are Republicans: https://www.cotton.senate.gov/imo/media/doc/tplinkfinal.pdf)
Lenovo (the computer company formerly part of IBM) also had a similar scare back in the 2000s, but they’re still around today and seemingly selling well. Shrug.
I think if the Chinese really wanted all our data, they’d just ask for it on TikTok and Fortnite…
OK I ordered a pair of MoCA adapters from Amazon last night, after my trip to Best Buy was unsuccessful. (And that story is better suited for the mini-rants thread in the Pit.) Looks like the kit comes with everything I need: the adapters, plus power supplies and both coax and ethernet cables. They should arrive on Saturday, so once I get everything set up I’ll report back in.
It was that simple for me, in two different use cases.
I use a pair of these between the master bedroom and the router:
That solved the issue of getting wired internet to the desk where my main computer is (along with Ethernet connections for any laptops I may also want to use there – I prefer to reserve WiFi bandwith for truly mobile devices and plug laptops into the wires network when possible).
I used another pair of those MOCA adapters when we installed fiber internet and then Optical Network Terminaton (“fiber modem”, as it were) was installed on an exterior wall across the living room from the router. This one, I had to reconfigure the adapters to use static non-routable (RFC-1918) addresses so that they wouldn’t try to steal the DHCP address assignment from the public fiber nerwork provider (since they’re on the WAN side of the router).
It all works a treat.
Do you understand how the coax terminations are? You have coax ports on the wall; the cables behind the wall jack have to connect to each other to connect the two MOCA adapters. For me, this was the biggest challenge. Our house is big and rambling and custom-built, and the original builders put several coax ports in each room (as the house was built in the early 90s and that was the state of the art at the time). Which is awesome for possibilities, but also meant that there’s a utility room in the basement with two dozen unidentified RG-60 cable ends, and I had to map out which ones went to the wall jacks I was interested in.
Yeah, our house is wired for cable, so everything within the walls should be connected. I’m 99% sure that when the office downstairs was my stepson’s bedroom that he had a cable box down there. So I’m not anticipating any issues… 
“Connected” means different things for coax than it might for Ethernet. Odds are good that those coaxes all connect to the output side of a splitter, which may or may not allow them to talk to each other.
In my case (as I mentioned), all the cable ends were dangling (since we cut the media cord and had no need for either CATV or satellite TV distribution gewgaws any more), so once I found the appropriate cable ends I just bridged them with a straight-through splice adapter like this.
Im contemplating doing something similar. Will wait for your story. I did read that splitters need to be compatible with the MOCA units, so something to pay attention to.
Yes. MOCA is higher frequency than CATV and splitters are passive frequency filters, so frequency incompatibility is something to look out for.
Like I just mentioned, I just spliced the cables together directly with a butt adapter which gives zero shits about signal frequency.
With the caveat that my experience with powerline adapters is with older technology and new models may or may not be more reliable, but a general comment about this tech is that it’s very much dependent on the specific environment. What works great in one house may not work in another, or may not work as well between different locations in the same house. Performance can also be affected by noise introduced into the circuit by some devices, like those using power factor correction (PFC) power supplies, or ovens, dryers, or air conditioners. If you experienced powerline adapters working very poorly or not at all, you may have been using them in circuits that were on different sides (phases) of the breaker panel.
My general advice is that if someone is going to go wired, direct Ethernet cabling is the best option followed by MoCA if you have suitable coax available. I would tend to stay away from powerline networking. Wireless is generally the most convenient, and depending on your coverage requirements and budget, mesh networks are generally highly regarded. My old computer in the basement is no longer networked, but when it was, I got the best results with a wireless bridge, which had large sensitive antennas and got a good signal from the router two floors up.
My MoCA adapters arrived today. Yay! So I took the box into front bedroom, where the router and stuff is, and started following the EZ setup instructions.
Step 1: Take one adapter and one ethernet cable. Plug the cable into the adapter. Check
Step 2: Plug the other end of the ethernet cable into the router. Check
Step 3: Take one coaxial cable and connect one end to the adapter. Check
Step 4: Connect the other end of the coaxial cable to the cable outlet. Che… um, wait. Where’s the cable outlet? I pulled three different bookcases away from the wall. There is no cable outlet! WTF?
Then I remembered… when we actually had cable service, the box where the cable came into the house was on the back corner, by where our main bedroom is. Three cables come out: one to the outlet in our bedroom, one to the living room (in the middle of the house) and one to the basement bedroom.
When we switched to ATT U-verse many years ago, they would only run a line to a room with an outside wall. So that front bedroom is where the fiber comes in now, but that room never had a cable outlet. 
So, I may be an idiot, but I am also a pack rat. I have a big box o’ cables in the basement, with old power cords, monitor cables, various A/V connectors, and yes… some coaxial cable! Including about a 55’ length.
So I think I can still lick this problem. I can go down in the basement and pull the cable that runs to either the living room or main bedroom, get one of those male-male adapter thingies, connect that length of coax and run it to the front bedroom and up through the floor. And then I have my cable connection in the front bedroom!
(I jokingly told my wife I was going to connect that fifty foot coax cable to the old cable outlet in our bedroom, then just run the cable down the hallway to the other bedroom. She threatened to divorce me if I did.)
And… success! I pulled the cable to our bedroom back down into the basement, and salvaged the male-male connector from the wall plate to use to connect my 50’ of coax cable and run it across the basement ceiling. I drilled a half inch hole in the floor next to the baseboard in the front bedroom and ran the cable up from the basement and connected it to MoCA adapter #1. I took the other one downstairs, hooked it up to the cable outlet and ran my ethernet cable to my work laptop, and it shows me connected to the corporate network (not on WiFi).
The real test will be a full day of work without any network hiccups. I’m actually looking forward to working tomorrow!