I made an assumption about your setup which may be wrong. I have only one device connected between the wall and my computer, which is both a modem and a wireless router combined, so I have just one thing to turn off besides the computer. When you headed your post with the phrase "Router, modem" I thought you were talking about one piece of equipment. If what you are talking about is a modem connected to the wall, which runs to a router, which connects to your computer (wired or wirelessly), then just follow the order mike kaiser gave you. Shut them all down, then start the modem, then the router, then the computer. With some systems, the order may not make any difference, and you can't hurt anything regardless of the order, but Mike's advice is the most logical approach: turn on the first thing in the chain that gets the signal, then the second, then the third (the computer).

Maybe you are using a usb connection now between the computer and modem? Login to the router and look for its DHCP configurations... hopefully you'll see its capable of handling more than one ip. I would have to assume it probably has full range of ip's. If so - All you really need is an inexpensive network switch, and some ethernet cables. Or rather than a switch you could add a wifi router configured as an access point, which would be inexpensive too. Or if you isp for some reason set the 4100 to fixed bridging mode, you can let it feed any router. Anything/everything will work standard ethernet connections. Mac, Windows, Unix, etc. ... everthing is capable of using standard ethernet connections to that modem/router. Your only problem is it only has the one ethernet port so you would at least need a four port switch. And sometimes you can buy wifi routers cheaper than standard network switches.

I’ve been doing computer work for over 15 years professionally and over 20 years personally Bc my mom did coding in the 80# for her job so I got started before all the people my age even had comps (im 34). I previously working for Comcast as an internet tech over the phone. I worked for them before they sent a lot of the support overseas and apparently quit putting money into their own employees training what reps are here.. my experience is 3 years with Comcast IP tech support tier 1 and 2, also a lead of an advanced resolution team. I’ve read all the comments above and before you change stuff I’m curious about a couple of things.. do you have packet loss and have you performed a trace Route? Besides your standard cable stuff and your neighbors, do you have any one in your area that you know of that has any external antennas or anything like that? They would likely be very old. Do your neighbors have any issues with their service? There is a lot of outside interference that can contribute to your problems unfortunately. I hate assuming but I am going to assume Comcast has come out, replaced your drop(line from the tap, green box or up on the power line, to the outside connection on your home), inside and outside wiring and modem/router. While the person mentioning about the WiFi channels is correct as far as that is concerned if you are having problems with other services of Comcast (phone and tv)? Do you? i do heavily agree with purchasing your own equipment. You can actually purchase an eMTA for your phone and a separate modem and separate router. If you choose to get separate modem and router, do not place them right next to each other or on top of each other. I recommend getting a short Ethernet cable and about a foot apart. They can interfere with each other. If you are using the standard modem band of 2.4ghz, I recommend any cordless phones be unplugged if not in use and any other items that use 2.4ghz. If your device has the option, always use 5ghz if you can. Ill hopefully be able to help. I hate the way Comcast customers want to make customers pay for service but doesn’t want to fix th problem when it’s down. Their techs are lazy most of the time or again they are outsourced contractors.

I have a free Spectrum modem too, at a second house. Because it was free, I paid no attention to the brand but I'm happy to accept your saying it's an Arris. You can be sure that any business that buys a product in large volumes, the tens and hundreds of thousands in this case, gets bids from more than one provider and everything else being equal, is heavily swayed in such decisions by price. I would come to no quality or performance conclusion about Arris simply because Spectrum provides them. It only means they were the lowest or one of the lower bidders. I have no investment in the one I use for Spectrum either financially or emotionally, if it starts to act erratically, I'll replace it. My assessment of Arris is based on the performance of a 3 year old unit in my primary home that worked poorly that I was more than happy to replace and whose replacement (a well rated Netgear model) has significantly better performance. No matter what, there's really no such thing as any tech company consistently being considered "one of the best in the business" across multiple product lines. Some are always better than others and lemons can be found from all of them. PS - Orbi and other so-called "mesh" system have their place but are overkill in many situations. I recently bought a new router for the smaller second home I have which, at a price 70% cheaper than what I paid for one Orbi (and I have two, counting the satellite) is perfectly adequate. That was why I asked chisue to describe the physical layout she wants to cover.