Question Ethernet randomly stops working ?

Dec 24, 2021
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This is mostly a copy-paste of a forum I started at a bad time (right before Christmas), but I have discovered something about the problem that I will add below.

This is a problem that I have had before. The ethernet connection on my desktop PC will suddenly lose internet but all other devices on the internet, wired or wireless, still connect and work just fine. The message in Windows network settings says that I can connect to other devices on my network, but it cannot reach the internet. Plugging in a Wi-Fi USB stick works just fine and it recognizes both my 5GHz and 2.4GHz networks.

Below are all of the things I have tried to fix this in the past and recently that have not worked:
  • Using Windows CMD to reset and flush the DNS and IP addresses.
  • Running Windows diagnostics.
  • Running a Network Reset in Windows.
  • Changing the DNS server in my ethernets IPv4 properties.
  • Trying other ethernet cables.
  • Turning off the ability for Windows to shut down devices consuming too much power / draining battery.
When the issued first occurred, my final attempt to fix it was reformatting my whole hard drive and putting a fresh Windows on it. When I did this, the issue was still happening. What fixed it was changing out the ethernet cable. The ethernet cable I had in it previously was working while plugged into my laptop just fine and wasn't dropping connection, but did not work on my PC before and after the reformat. This time, I have two cables that are fully functional and work in every machine in my house except for my desktop. I do not want to go through the hassle of reformatting again only to find that it didn't fix the problem.

Update: My ethernet suddenly started working again. After being on Wi-Fi for 5-6 days and changing absolutely nothing on my PC, I plugged in my ethernet to see what would happen and it just started working. Only two days later, it stopped working again with the same message. Again, plugging in my primary ethernet cable or any other ethernet cable I have into my laptop works just fine and never drops the connection, it's just my PC.

My motherboard: ASUS ROG Strix B450-F Gaming II

Any help or suggestions would be appreciated. Thank you.
 
Can you tell if the ethernet port is actually going down. Do you get a red x icon, if you do IPCONFIG /all does it show disconnected.

If the port is actually going down that is almost always a hardware issue. It is either going to be the cable or the port in the machines. Since you can't fix the port you need to hope it is a cable.

Be very careful about ethernet cables. There are a massive number of fake cables being sold. Many people are buying those flat cables which do not meet ethernet standards and some device do not tolerate running on those cables consistently.

You need cat5e or better cables but more important is the wire must be pure copper (no CCA) and must have wire size 22-24, those flat cables are 30-31 which is way too thin.

The easier way to check a software issue is to get a linux boot image on a usb stick. These run completely from the USB and do not touch your drive. They have basic web browser installed but in your case that should be more than enough.
 
Dec 24, 2021
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Can you tell if the ethernet port is actually going down. Do you get a red x icon, if you do IPCONFIG /all does it show disconnected.

If the port is actually going down that is almost always a hardware issue. It is either going to be the cable or the port in the machines. Since you can't fix the port you need to hope it is a cable.

Be very careful about ethernet cables. There are a massive number of fake cables being sold. Many people are buying those flat cables which do not meet ethernet standards and some device do not tolerate running on those cables consistently.

You need cat5e or better cables but more important is the wire must be pure copper (no CCA) and must have wire size 22-24, those flat cables are 30-31 which is way too thin.

The easier way to check a software issue is to get a linux boot image on a usb stick. These run completely from the USB and do not touch your drive. They have basic web browser installed but in your case that should be more than enough.
From what I'm seeing, nothing is showing that the ethernet port is down when it is plugged in. Everything seems to be connected, it recognizes exactly which IP address the router gave it, etc. Everything looks normal about it except for the fact that it just suddenly stops working for no reason.

As for the cable quality, this is an old Cat5E cable that we've had for probably 6+ years and it has worked in every machine just fine. It works in the other two desktop PC's in my house without a problem and both laptops as well. It does work on my computer as well and always has until this issue started happening.

As for it being software, I really can't say right now. I still have a bootable Linux USB drive sitting around somewhere that I can try, but I doubt that'll show anything. Previously, I had reset my Windows to try and fix this issue thinking it was a software issue as well, but the issue was present from the moment I booted into a fresh installment of Windows 10. And no it was not the built-in Windows reset that keeps your documents. I reformatted the whole drive and started from scratch and the issue was present the moment I booted in.
 
Leave a ping run to the router IP address and see if that fails.

If that works you start to suspect the default router is getting messed up. Try to hardcode the IPv4 address/gateway/dns rather than use DHCP. Be sure to disable IPv6 just to make sure it is not causing issues.

Use the ARP command and see if anything strange is going on. If the mac mapped to the router would change it can cause issues.

If nothing still works try to clear the ARP table. Then ping the router IP. Even if the ping fails what you are looking for is if the ARP table is repopulated. This is such a basic thing that you start to suspect a hardware issue if the port is actually active but ARP fails.
 
Dec 24, 2021
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Leave a ping run to the router IP address and see if that fails.

If that works you start to suspect the default router is getting messed up. Try to hardcode the IPv4 address/gateway/dns rather than use DHCP. Be sure to disable IPv6 just to make sure it is not causing issues.

Use the ARP command and see if anything strange is going on. If the mac mapped to the router would change it can cause issues.

If nothing still works try to clear the ARP table. Then ping the router IP. Even if the ping fails what you are looking for is if the ARP table is repopulated. This is such a basic thing that you start to suspect a hardware issue if the port is actually active but ARP fails.
Ok well... I found the issue.

The issue is literally our router. Just 25 minutes ago, we had another spike of internet lose, but now my Wi-Fi stick was giving the same message and another desktop suddenly started getting the message. After rebooting our router (which I have scheduled by default), every device started working. Rebooting our router is something I do at a decently regular rate and give it software updates, but these past 2-3 weeks it's just been a bit more fidgety.

Thanks for the advice!
 
Dec 24, 2021
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You should not have to reboot the router I have had mine on continuously for well over a year at a time.
Believe me, it's odd. The router did also receive a firmware update that night it resolved itself, but I have a hard time believing that just one firmware upgrade fixed an entire issue that only became present after having the previous firmware rendition for around 2-4 months with no updates.
 
Dec 24, 2021
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If you have to keep restarting your router on a regular basis to restore internet connectivity, it's time to replace it.
The router I bought isn't even that old. We've only had it for just over a year and it's been fine up until recently. Yes a reboot and firmware upgrade fixed it for now, but other good routers at the moment are just too expensive.

The router I have now is a TP-Link Archer A7.
 
I never would let any option enable that let a router get firmware by itself. I guess if its working that is all that matters. Maybe it attempted a firmware update previously and somehow failed.....or was constantly trying to upgrade and kept taking your internet down.
 
Dec 24, 2021
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I never would let any option enable that let a router get firmware by itself. I guess if its working that is all that matters. Maybe it attempted a firmware update previously and somehow failed.....or was constantly trying to upgrade and kept taking your internet down.
The router doesn't do automatic updates. If it did, I would have turned them off. The update that I had done had just recently become available and that's what fixed my issue. Normally I can go a long time without dare updating it, but for some reason, the previous version just started having problems that only became present after months of no updates.
 

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