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Ethernet broken but WiFi working - please help

kmw350
Grafter
Posts: 203
Thanks: 9
Registered: 17-09-2010

Ethernet broken but WiFi working - please help

I'd really appreciate some help here, I'm baffled over this.

My PlusNet connection has worked fine for years- consisting of Ethernet to 2 x desktop pcs, and wifi to several other devices, all from the same router.

Yesterday morning Sat 6 Aug, the internet began disconnecting, and has done so EVERY couple of minutes ever since.

 

I phoned the PlusNet helpline, and [CSA Removed] gave me good advice, and I have gone through many steps, but am now baffled. Here's what I have done/discovered:

 

If I unplug all Ethernet cables from the router, the broadband & internet connections are re-established and I can use wireless internet without any problem. However, plug any Ethernet cable back in, and I immediately lose my internet connection again.

So, thinking this meant the router is faulty, I tried another router (which I believe to be ok) - exact same problem.

 

I have tried 3 Ethernet cables; 2 x desktop pcs; 3 filters; 2 routers; ran the tests from the master socket.

 

How on Earth can it have been fine on Friday evening and now lose connection, but only when Ethernet is plugged in?

 

I should add, the connection drops as soon as an Ethernet cable is plugged into the router, EVEN IF the pc is switched off.

 

It just doesn't seem logical that both routers can have suddenly developed the same fault, so please, can anybody shed some light on this?

Moderator's note by Mike (Mav): CSA name removed as per Forum rules

30 REPLIES
PeeGee
Aspiring Pro
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Registered: 05-04-2009

Re: Ethernet broken but WiFi working - please help

I'm assuming there is no separate switch in circuit. What happens if you unplug both ethernet cables at both ends, then plug each cable into the router (singly, and then both together). If that's ok, then plug the cables into each computer one at a time, then both. Report back here.

Phil

 

 

Plusnet Fibre (Sep 2014), Essentials (Feb 2013); ADSL (Apr 2009); Customer since Jan 2004 (on 28kb dial-up)
Using a TP-Link TD-W9980 modem-router.
kmw350
Grafter
Posts: 203
Thanks: 9
Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

I can plug an ethernet cable into the router (whils it is NOT connected to a pc), and the connection remains ok - all lights are green.

The moment I plug the cable into a pc (EVEN if that pc is off ), I lose broadband/internet lights.

 

This happens with two different pcs, and with two different routers.

 

Thanks for any help.

Baldrick1
All Star
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Registered: 30-06-2016

Re: Ethernet broken but WiFi working - please help

You're not accidentally plugging into a WAN port instead of a LAN port on the router are you?

Community Veteran
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Registered: 16-02-2009

Re: Ethernet broken but WiFi working - please help

You wouldn't happen to have 2 different mains circuits would you? With the router plugged into one and the pc's the other.
Have seen that problem when they were on different phases. But can't think why it would suddenly occur.

Can you physically move the router plug to the same connection as the pc's?
kmw350
Grafter
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Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

No, thanks for asking, I have just double checked and I promise I am plugging into the correct ports.

 

Just to clarify something I said earlier, when I said the pcs were turned off, they were in standby, so there was still power from the electricity supply. If I turn them off at the mains socket, then I still have all green lights on the router. As soon as the pc is turned on at the mains socket, I lose internet light on the router.

 

Again, this applies with both pcs, and with two different routers (Thomson TG582 & 585 models).

 

It's almost as if there is some kind of static or power loss killing the connection if any Ethernet cable is plugged in.

 

PeeGee
Aspiring Pro
Posts: 1,081
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Registered: 05-04-2009

Re: Ethernet broken but WiFi working - please help

The only time I have seen that effect, two computer were connected to one router port via an automatic switch.

Has the router separate indicators for the ports? When you connect a PC, do the lights flicker continuously? That could indicate a loop with the router attempting to get routing information from a recursive loop - you can see the effect by plugging both ends of a cable into the router. It doesn't cause harm, but slows traffic to an effective stop due to the amount of priority traffic.

 

 

Plusnet Fibre (Sep 2014), Essentials (Feb 2013); ADSL (Apr 2009); Customer since Jan 2004 (on 28kb dial-up)
Using a TP-Link TD-W9980 modem-router.
kmw350
Grafter
Posts: 203
Thanks: 9
Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

Thanks HairyBiker, but they are plugged into the same double mains socket.

 

 

Community Veteran
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Re: Ethernet broken but WiFi working - please help

Have you bought any new appliances lately and do you have RCDs in your Main Distribution Unit?

kmw350
Grafter
Posts: 203
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Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

I'm sorry I don't know anything about an automatic switch.

They are completely separate desktop pcs, plugged into the same router via their own Ethernet cable.

The router has 4 Ethernet sockets and they each have their own indicator light, which lights up green when it is connected to a pc. It's always been a pretty solid green once plugged in, as far as I can recall, though now I have them completely removed in order to use the internet.

 

I am thinking I should nip to Argos and try a brand new router to see if it solves the problem.

 

 

Community Veteran
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Registered: 16-02-2009

Re: Ethernet broken but WiFi working - please help

you got anything else with an ethernet port on it?
Or the other router would work.
Plug the other router into the mains (not the phone). Connect a cable between them both. If same thing happens then problem lies in the router/cable. If it stays up and both routers have a link light on then it is a problem with the pc side.

If it stays on and the light is solid/wifi fine then we need to look at the pc side.
kmw350
Grafter
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Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

We haven't added any new device lately, and I just checked the main electric cupboard - there is an RCD in there. I can't think of anything that would have changed the load.

Thanks for asking.

Community Veteran
Posts: 5,077
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Registered: 16-10-2014

Re: Ethernet broken but WiFi working - please help

Before you go out to the shops, I assume you have tried the other ports on the router? You said you had 4 have you tried them all? If you do buy a new router buy a couple of CAT 5/6 cables as well and try them first before you break the seal on the new router. So if it does work, it's easier to get your money back.

Also, do you have any pets? The type that like to eat wires? As these seem to be the common factor in all the tests that you've done.

kmw350
Grafter
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Registered: 17-09-2010

Re: Ethernet broken but WiFi working - please help

I don't have anything else with an Ethernet port, but I did what you suggested and connected the two routers together.

A link light lit up on each of them, and all lights stayed green on the first router. All lights except internet light came on on the other router.

 

I've checked my cables, they all seem solid, nothing chewed or crushed, and the same problem was with 3 different cables, and in all Ethernet ports.

 

Some kind of static problem?

If you good people think it's a problem in my house rather than at the exchange or elsewhere that requires a fault check, then maybe I should just connect wirelessly and not worry about it?

Community Veteran
Posts: 6,653
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Registered: 16-02-2009

Re: Ethernet broken but WiFi working - please help

Since it only affects your pc's and not your internet connection then is not an exchange issue.
Since the two routers are happy connected together then it is not a router or cable issue.
That leaves the PC's. Try changing the power leads to new ones (or off a different thing not the other pc)
If that is the same, the remove all the connections to the pc, and plug it in to the router, then add the power cable and see if it still has issues, continue till you find something that causes the issue.