In reply to a post by joconnell:

Kaspersky,

If you can, uninstall. Don't disable, you have to remove.

May I ask a stupid question of the OP, please?
I certainly don't want to teach anyone to suck eggs.

I had this problem years ago, and I changed my cables pinout to a different way and it worked a treat. I am unable to find the original diagram that I used to carry in one of my cases for future reference, but I found a similar one.

We should all know about T568A & T568B types of pinout, here is a simple three option guide, which looks similar to the one that I used to use!
Hope it helps, certainly worth it if you have the kit. https://www.pinterest.co.uk/pin/696017317397807377/
PLEASE don't confuse this with the common phrase of a "Crossover Cable" as T568A & T568B both have Crossover pinouts!

If you have the kit to do your own wiring of Cat 5e or whatever and some RJ45 males around it may well be worth trying as it definitely worked for me, OR, triggered something in the Drivers or Windows, that made it work much better and faster!
Either, you decide! I still don't know to this day why such a simple change should make such a huge difference, but it did!

I take it you are going straight from one PC/Laptop to another PC/Laptop?
In which case it is the identical problem that I had and this cured it first time!

In reply to a post by TrevorSP:

May I ask a stupid question of the OP, please?
I certainly don't want to teach anyone to suck eggs.

I had this problem years ago, and I changed my cables pinout to a different way and it worked a treat. I am unable to find the original diagram that I used to carry in one of my cases for future reference, but I found a similar one.

We should all know about T568A & T568B types of pinout, here is a simple three option guide, which looks similar to the one that I used to use!
Hope it helps, certainly worth it if you have the kit. https://www.pinterest.co.uk/pin/696017317397807377/
PLEASE don't confuse this with the common phrase of a "Crossover Cable" as T568A & T568B both have Crossover pinouts!

If you have the kit to do your own wiring of Cat 5e or whatever and some RJ45 males around it may well be worth trying as it definitely worked for me, OR, triggered something in the Drivers or Windows, that made it work much better and faster!
Either, you decide! I still don't know to this day why such a simple change should make such a huge difference, but it did!

I take it you are going straight from one PC/Laptop to another PC/Laptop?
In which case it is the identical problem that I had and this cured it first time!

All my wiring is cat5e terminated according to T568B, I did it myself when the cabling with first installed, tested it using LAN testing hardware and it all works.

I'm going from desktop PC to laptop, indirectly connected via a managed switch.

In reply to a post by jchamier:

In reply to a post by joconnell:

Kaspersky,

If you can, uninstall. Don't disable, you have to remove.

I'll try that on both machines.

My bad,
I missed the switch part, I thought you were going directly from one t' other!

Thanks to everyone who responded to this thread, I was about to uninstall the AV and anti-malware software from both PCs when I retried the tests and now all seems well. iPerf3 in either direction reports around 950Mbps and copying files from one PC to the other in either direction happens at a speed of around 105Mbps. Just to be clear, I didn't disable or uninstall anything on either PC, though both machines have ben through a Windows update since I first posted here, so maybe that made a difference?

Thanks again

In reply to a post by joconnell:

though both machines have ben through a Windows update since I first posted here, so maybe that made a difference?

As one is a MS Surface, that is more likely since these machines receive driver updates through WU.

Good to know the speed is at a normal level!