I have a fairly simple network setup,

  • Netgear CM1200 cable modem in master bedroom
  • Wired Ethernet throughout the house
  • Netgear R6700v3 wifi router connected to wired wall Ethernet in second bedroom
  • Computer (Windows 10) connected to the router via wired ethernet (NOT WIFI)
  • Cox gigablast (940 mb/s internet plan)

My problem is I'm getting terrible download speeds. Sometimes on speedtest.net I get 150mb/s but mostly I get 20mb/s and sometimes I get < 1mb/s. I also get a lot of packet loss.

My ISP is saying everything should be good so I want to run tests within my home to verify that its not my house wiring, or my router, or my cable modem. Is there any way to diagnose and verify everything is ok in the house?

I did a simple test where I unplugged my router and plugged in a laptop directly into my cable modem and I got 80 mb/s down.

How do isolate each component one at a time? Thanks!

  • You don't indicate if those speeds are on Ethernet or WiFi. Depending on if what version of WiFi you are talking about you might be hitting the limits of your networking hardware. If you connect your computer directly to the modem does are the speeds what you expect? – Ramhound Mar 26 at 0:37
  • Thank you @Ramhound I updated the post to mention the computer is connected directly to the router wired (not wifi) – coderdave Mar 26 at 0:38
  • I also mentioned connecting the laptop to the cable modem I get 80 mb/s down. I also noticed I had to unplug the router and reboot the modem - can you not have a router and a laptop plugged into the modem at the same time? – coderdave Mar 26 at 0:39
  • What sort of ports does your computer and laptop have? Ethernet cable is not all created equal. What is specifications is your Ethernet cable? – Ramhound Mar 26 at 0:53
  • How do I determine what type of port I have on my computer and how do I determine the specification of the ethernet cable? Thank you! – coderdave Mar 26 at 1:13

The only way to test the entire home network without expensive software or hardware is to take your laptop and plug it directly into each router, hub, and switch, and run a speed test through each one. The bandwidth you get on the speed test also depends on how much of the Internet in your home is currently in use. If you want the most accurate test, run the test on each piece without anything else connected to them.

FYI on the comment on the original post: You cannot have multiple pieces of hardware connected on the Internet of a modem without some type of router between the devices. If you just use a splitter, hub, or switch, two of the devices will create a feedback loop and block everything as they will have the same external IP address from the modem. This is because modems are designed to pass their external IP address off to the next piece of assignable hardware. Whether that is a computer or router doesn't matter. It is the router that gives all connected devices their internal IP address and connects them to the Internet. It gets more technical, but that is the rundown.

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  • That's surprising that there isn't free open source software that can monitor and test the health of the network. I appreciate the answer and I'll test with a laptop moving around. The shitty thing is that the network speed isn't always slow sometimes its fast but then other times its slow so I can't see at two points at the same time if its just one access point or if its the entire network – coderdave Mar 26 at 0:48
  • Also, thank you for explaining to me why connecting a router and laptop to my modem doesn't work. – coderdave Mar 26 at 0:50
  • My cable modem supports 4 devices. So my comment isn't that crazy. – Ramhound Mar 26 at 0:50
  • That's because your modem is classified as a modem/router gateway. It has a router built into it. A standard modem only has one Internet port. – Tytus Strube Mar 26 at 0:55
  • @TytusStrube - Netgear CM1200 has 4 Ethernet ports. – Ramhound Mar 26 at 1:18

You could have a bad line. Verify you don't have any splitters between modem and where signal comes into the house. Or if you do verify with ISP that the attentuator is necessary.

Laptop directly connected to modem should be close to 850 mb/s. Swap ethernet cables, they should all be at least CAT 5e (Gigabit ethernet). Cat 5 is not Gigabit.

All your equipment is Gold Standard, so no reason to not be near 85% of rated speed. ISP should come out and do a line test.

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