[SOLVED] Slow internet speed when one device downloads over LAN

[Matty_od]

Hi everyone wondering if you can help me figure this out. We're on Virgin media and get about 350mb/s download. We have two PC's one connected directly into the router with a CAT5e cable. The other is downstairs and plugged in via a powerline adapter. When the PC with the powerline adapter is downloading (say a game on steam at about 20mb/s) the other PC that is plugged in directly gets about 1.5mb/s.

Do you have any idea why this is happening and how we could fix it? We used to have this setup in our old house with the same router and had no issues. Do you think this could be a problem that our ISP has caused when re-registering our router? I've tried contacting them but with the state the world is currently in I've been on hold for about 3 days now!

I've tested this with a Laptop plugged into the same cable the pc having issues is and it also gets the same issue. I have also tried a differnt cable and that has also not worked. It seems like when the one pc is downloading anything else connected via LAN suffers too. I have not noticed any devices that are connected via WI-FI having trouble.

 

[Ralston18]

Make and model modem and router? Or modem/router if combo?

Do verify that the hardwired (ethernet connected) computers have only their respective ethernet adapters enabled. Their wireless adapters (likely on the the laptop) should be disabled.

Who has full admin rights to the router? The router's logs (if available and enabled) may prove helpful?

 

[Matty_od]

Make and model modem and router? Or modem/router if combo?

Do verify that the hardwired (ethernet connected) computers have only their respective ethernet adapters enabled. Their wireless adapters (likely on the the laptop) should be disabled.

Who has full admin rights to the router? The router's logs (if available and enabled) may prove helpful?

It's alright after extensive testing with a laptop we've figured out that it was indeed the powerlines causing the problem because they were on a different circuit. I have no idea how or why that would effect the other pc that was connected via Cat5 however if some wizzard would like to explain that, it would be great! The only solution to this that we can think of is just buying a long cable and connecting it up to the router directly.

 

[Ralston18]

Not a "wizard".

Explanation: "Gremlins".

Actually, powerline adapters on different circuits (breakers/fuses) are inherently problematic.

"Problematic" often holds true for even being on the same circuit; any sort of issue could and will slow speeds.

Could be that some connection within any given outlet is just not as clean and tight as is should be.

And/or the wiring is old, deteriorated, or damaged and resisting the necessary signals. Could even be the circuit breaker if not the wiring.

An electrician may be able to test and discover some problem but there are no guarantees that fixing that particular problem will help.

Try the long cable but only as a temporary/test solution. If all is well then the culprit is very likely the house circuit/wiring.

Then you can make a fully informed decision as to how you wish to or need to proceed.