I would install Wireshark on the affected PC(s) and when you get hit by
a speed drop run wireshark see what all the chatters is on the net port
is. Other things to try swapping the ports around on the switch from the
affected PC(s), Try swapping cables around and see if the problem
follows the cable or the port swap.
Tim H
On 20/07/2025 10:25, rmluglist2--- via Hampshire wrote:
>
> Hi all
>
> Having upgrade to fibre recently, I’ve started to experience a weird
> problem with the speeds I’m getting. More details below but does
> anyone recognise the following issue? For some reason, speeds of
> 800+Mbps suddenly drop to around 90Mbps on certain machines only. I
> have no managed switches so why it should suddenly “throttle down” is
> beyond me. When it does throttle down, I’ve proved it doesn’t affect
> every machine on the network – only those in a certain room.
>
> I have found a solution – to manually change the cabling such that it
> bypasses a couple of switches – but I maintain – I can still get the
> 800+Mbps even using the switches that I later bypass to return the
> connection to its correct level. So, to summarise, it’s 800Mbps,
> drops to ~90Mbps, change ethernet cable to bypass a couple of
> switches, speed rises to 800 again, put cabling back to its original
> and still get 800.
>
> Here’s a bit more detail: My study is in a converted garage at the
> rear of the property. All machines in the house (separate from the
> garage) always maintain 800Mbps. When my main machine (located in
> the study) slows to 90Mbps (and other machines follow suit), I bypass
> any other switches in the study and connect it directly to the
> ethernet cable feeding the study from the house (where the router is
> located). In so doing – bingo – I’m back to 800Mbps. I then put
> the cabling back to the way it was prior to the drop in speed and can
> still achieve the 800.
>
> So somewhere, it (one of the switches by the looks because it’s not
> only one machine that’s affected) is going into some sort of “mode”
> where it throttles bandwidth. But I maintain none of these switches
> are managed so why would this be happening?
>
> Yours tearing my hair out
>
> Rob
>
>--
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