Question LAN speed is always changing from 2.5Gbps / 100mbps to 10mbps ?

[manoj17]

A few months ago I built a PC

PC Specs
Mobo: MSI PRO B650M-B
CPU: Ryzen 5 7600,
RAM: 16GB
Storage: 1TB SATA SSD
PSU: 650w

Since its a non-wifi mobo i installed a USB network adapter. Everything is ok but i am facing problems regarding LAN Speed. I have also connected my pc with LAN cable, hoping i would get good speed with this. But the problem is that when i connect my pc with LAN cable it is giving only 10Mbps. So i changed the speed and duplex value to 2.5Gbps full duplex. But after few minutes the speed and duplex value automatically changed to 10Mbps.

I thought my LAN cable was faulty so I changed it with a new one having same Cat 6e certification but nothing happened. I'm still getting 10 Mbps speed (changing from 2.5Gbps).

Now i removed the cable from the pc and connected it with my gaming laptop, i found out that the laptop is getting good speed from the same LAN cable (that means there is no defect in cable).

I thought problem is in my mobo, but i took my PC to another place and connected my pc with LAN Cable. ThereI found out that my pc is giving good speed, nearly 100mbps.

So now i don’t know what is really causing the problem. Mobo is good, LAN cable is good.

What could be the problem?

 

[bill001g]

What do you mean you took the pc to another place. Are you connecting the cable directly to a router or switch or are you using cables that run though a wall.

You really need to hope the problem is a bad cable. The speed negotiation is done at a very low hardware level testing tiny electrical voltages. Although it is kinda software it is something that is set when the ethernet chip that is on the motherboard was manufactured. You would have to replace the whole motherboard, maybe someone with one of the $1000 motherboard might pay to have it fixed.

Good news this problem is like 99% of time just a bad cable. First there is no such thing as cat6e. There is cat6 and cat6a. There are massive amounts of fake ethernet cable sold. The most common is that flat cable that has wire much too thin to meet the standards to be certified as a ethernet cable. Even the very best cable can get damaged or go bad.

Testing on different machines mean very little unfortunately. Some machines tolerate cables that are out of spec much better than others.

There is no effective way to really test cables in a home or even small business environment. Meters that can actually test that a cable meets the standards for a ethernet cable to be certified are out of the price range that most people would consider. These meters are generally only owned by people who install ethernet cables for a living.

The cheapest thing to try is to buy a new cable. Even at 2.5g you need nothing special. Cat5e will function at those speeds. The key thing to look for is the cable is pure copper cable with wire size 22-24. All vendors know about the fake cables. Good vendors will always have this information clearly displayed. If you ran 10gbit you want to buy cat6a. You can consider cat6 but only if it is cheaper than cat5e it will not run any different or better than cat5e. Most other cable with other numbers is fake.

 

[manoj17]

I took my pc to another place -- Means i want to test pc with another network ( I thought bad network is causing this issue).
But there it performed well and gave 11-13 mb/sec download speed.
Sorry for writing error, i was writing just Cat 6.

View: https://www.youtube.com/watch?v=3MNWRYHH97M

 

[bill001g]

Maybe the first question would be why it is not gigabit speeds. Unless you have a extremely old router it should have gigabit ports. Many/most newer motherboards have 2.5g ports.

Theoretically if you had a extremely old router it could have 100mbps ports.

The main reason a port runs at 100mbps rather than 1gbit is because there is some issue with the brown or blue pair of wires (assuming standard wire colors). 100mbps can run on just 2 pair of wires. When it drops to 10mbps it means the port is getting so many errors running at 100mbps that it will try 10mbps.

Again this is all done in hardware. The only thing you can really do is force it to run at a slower speed. You want to leave it set to auto for best results.

If you are absolutely sure your cable is good then I would look at a PCIE ethernet add in boards. These are fairly inexpensive. You could also consider a USB ethernet port but make sure you have a free USB3 port or it will top out at about 400mbps.

Again the cheapest thing to try first is a new quality cable.

 

[evermorex76]

I've never heard of a NIC changing the link to 10Mbps when you've hard-set the speed in the settings to be something else. It should just fail to connect. How are you determining that it has changed? Are you setting the speed via the device properties?

What equipment are you using? Router, switch, models? Did you try all the ports on the device, too? Do you have the latest motherboard BIOS installed, and the latest network controller drivers from Realtek? How long are the cables you're using and are they going directly to the router/switch?

When you tested the "good speed" at the other place, what was the actual link speed of the interface? Were you testing to an Internet server and that site's own Internet service was only 100Mbps which would limit the test results?

It's totally possible that the port on your motherboard is just bad. Poor soldering of the pins in the socket, or damaged at some point when connecting a cable, something like that. If your Internet service is less than 1Gb then just get a Gigabit PCIe card for testing. A 1Gb card is $15 on Amazon, or heck a "Brostrend" 2.5Gb card is only 18 at this moment and probably has the same Realtek chip that more expensive cards have and may even be made at the same factory with the same parts. A USB3 Gigabit adapter will also perform very well and can be only $10. Order a good Cat5e or Cat6 cable at the same time, branded Monoprice or Cables to Go or Startech or Cable Matters, any known name brand that is still not a rip-off price just for the brand name.

 

[Dashhh]

Can you please provide us the model of your USB network adapter and router?

 

[Ralston18]

And I will add the suggestion to run "ipconfig /all" (without quotes) via the Command prompt.

Ipconfig is a diagnostic tool that can reveal a variety of problems.

You should be able to copy and paste the full command results into a post here without needing to retype everything.