Internet download speed is slower than it should be

[JesseZ]

Hello!

I have comcast xfinity internet and one day the internet just became super slow. I used speedtest.net and the download speed is around 20mbps when it is supposed to be around 100mbps. After 2 phone calls, 2 service visits, the issue is still there. I have a Gigabyte GA-970A-UD3 motherboard with a Lan port.

The steps I've taken to solve the issue have been:
1. changed the cables to test if they were bad
2. got a new netgear R6400 router replacing an old netgear FS105 switch
3. Some other steps that I can't even recollect but I'll try to clarify.

My question is what could be causing my internet download speed to be so slow in comparison to what it should be? Could my Realtek PCIe GBE Family Controller be misbehaving?

 

[Someone Somewhere]

Do other devices on the same network show similar speeds? Using the 'share' button on Speedtest works best for this.

 

[JesseZ]

Do other devices on the same network show similar speeds? Using the 'share' button on Speedtest works best for this.

Yes, I have a computer that one room away from the router (wired in) and a computer in the room with the router (wired in) and both show similar speeds. Additionally when we first plugged in the new router it showed speeds of 120, but then 20 mins later it showed speeds of 20 mbps download.