Question Problem with fiber lan speeds

Mar 5, 2022
Hi all,

Just set up a fiber connection for a small company and that is supposed to give near 1000/1000 download/upload. I am currently testing the speeds on my work laptop, server, and spare laptop. Regardless of where I'm connected, it seems like all speeds are the same.

Connected to network jack that is connected to switch.
Connected directly to switch.
Connected directly to firewall.
Connected directly to router.

My work laptop is the only laptop that is receiving consistent speeds at 900+/900+ down/up which is acceptable, but however, the server and spare laptop speeds are both 900+download/40-60upload. I've called the ISP and they ran tests on their core and everything seems to be normal on their end regarding what is stated in the SLA. 900+/900+.

Attempt to troubleshoot:
  • Update NIC drivers
  • Reinstall NIC drivers
  • Changed speed & duplex setting from auto-negotiation to 1gb full duplex
  • Used multiple sources of speed tests giving back similar results
  • Firewall is set to Full Duplex Auto-Neg
  • Both server and spare laptop NIC settings are up to 1000/1000 mbps
  • All cables used are cat6 cables
What's weird is how my work laptop is able to get the speeds but not any other devices. Any thoughts?

My question is: Would anyone know the reason why the upload speeds are so low?
If any device functions then it almost can't be the ISP. The router hides all the machines and they all appear to come from the 1 IP that was assigned to the router. Even the router should not have different speeds for different machines. I will assume there is no QoS or firewall setup in the router.

This almost has to be some software on the pc. It is strange it is more than 1 pc.

What I would first do is test by coping files on the lan between the machines. You may not get 900mbps because of disk bottlenecks but you should get a couple 100mbps minimum. You can see the speed the network tab of the resource monitor. Be careful some of the numbers are MBYTES.

The other option would be to test using a old line mode tool called IPERF. This tool is not affected by cpu/disk/memory etc. You should see speeds in the 900mbps range in both directions. You need to load the software on 2 machines and set one to server and the other to client.

If this all works on the lan then it is going to likely be something strange with maybe the browser or maybe there is some kind of software loaded. Programs that claim to favor or prioritize certain traffic tend to be the ones that cause strange issues like this. If you have anything like that installed you want to uninstall it or at least disable it.