Internet For Entire Home Goes Out When I Plug Ethernet In

[Inglorious]

Nighthawk AX4500.

Topic, when I plug the Ethernet cable into the router for my PC, my entire internet including wifi goes out. Internet went out at 3 PM yesterday, it is 5:43 PM and I have had wifi for an hour uninterrupted without Ethernet plugged in. Friend who was a ISP service tech helped me get it to this point but we have no idea why the Ethernet cable makes it all go out.

[CrimpOn]

First step is to try a different Ethernet cable.

Is the PC connected only to the router with a cable? (no simultaneous connection to anything else, even over WiFi?)

Are there any Ethernet switches involved?

[Inglorious]

No switches involved, I do use two cables and a splitter. Will try using different cables as my next step if it doesn't work tonight when I plug in again. That didn't come to the top of my mind just because if it's causing the entire internet including wifi to go out I thought it IP or router itself related.

[CrimpOn]

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@Inglorious wrote:
I do use two cables and a splitter.

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Please explain this in more detail.

In the days before gigabit Ethernet, it was common to use two pairs of a cable for one Ethernet connection and the other two pairs for a separate Ethernet connection.  Gigabit Ethernet requires all four pairs, so this technique no longer works.

[Inglorious]

Sure -- the router has to be in a different room so my PC is connected with two cables via a splitter to reach.

[CrimpOn]

Splitter is a very specific term.  They are normally deployed in pairs

Can you attach a picture?

[Inglorious]

this is what I mean. I had my Ethernet cable unplugged for 4 hours with 0 issues. Within a minute of plugging my desktop back in my entire network went down again.

[CrimpOn]

Thank you for the picture.  That is what is usually called an "RJ45 Coupler" (not a "Splitter").This is a most unusual situation.  With the problem happening when the desktop computer is connected to the router, the obvious areas of concern are:

• The computer, or
• The cable.

What I (personally) would do is purchase a 100ft Ethernet cable from Amazon (under $20US) and connect the computer directly to the router using this cable.  (The family will shriek, "what are you DOING???" and you will reply, "It's just for a few minutes. Please don;t trip on it.")

I would also look very closely at those tiny gold wires in the RJ45 jacks (router and computer).  Maybe one of the wires is bent.

[Inglorious]

I'm going to get a cable and a USB to RJ45 adapter for the PC. I tried all four ports on the router and the issue persisted when it plugged in, so if the router isn't the problem I'm confident I narrowed it down to cable and PC with your help. Will report later!