Gigabit Ethernet Periodically dropping to 10/100.. rebooting switch restore gigabit?

Scythe · 14 Jan 2021 at 09:00

Hi,

I have recently had Cat6 ethernet installed in my home and things were working great, but I am occasionally seeing the speeds at switch 2 drop to 100mbps.

When the speeds have dropped, a check of all switch ethernet ports are showing green LEDs indicating gigabit speed. If I reboot switch 1, Gigabit ethernet speeds are restored to devices at switch 2.

My configuration is as follows:
Router > Switch 1 (Xbox, Sky Q, TV) > Switch 2 (NAS, PC, Laptop). The switches are both TP-Link TL-SG108S 8-port unmanaged switches.

Can any network gurus advise what could cause a stable gigabit line to drop to 100mbps?

Could the presence of specific devices could it to drop? I ask as I rebooted the switch last night and watched TV on sky only. I woke up to find the devices at Switch 2 had dropped to 100mbps again!

the-evaluator · 14 Jan 2021 at 09:13

Iffy cabling or termination I would expect. I've seen it happen several times. A basic cable continuity test shows that all is good but a more detailed test that's looking at more than continuity picked up a few issues.

Rather than rebooting the switch, what happens if you unplug and plug in again the cable? It could be a problem with the switch, so try swapping the uplink to a different port and see if the problem follows it.

Scythe · 14 Jan 2021 at 09:26

the-evaluator said:
Iffy cabling or termination I would expect. I've seen it happen several times. A basic cable continuity test shows that all is good but a more detailed test that's looking at more than continuity picked up a few issues.

Rather than rebooting the switch, what happens if you unplug and plug in again the cable? It could be a problem with the switch, so try swapping the uplink to a different port and see if the problem follows it.

Will do, just got to wait for the speed to drop again now.

the-evaluator · 14 Jan 2021 at 09:29

It's also worth swapping out the patch cables at both ends to see if that makes a difference.

Avalon · 14 Jan 2021 at 09:54

My first thought is poor termination on either end of the uplink, presumably this is to a central patch panel and faceplate on each run? Depending on the practicality and frequency of drops can you bypass the uplink run on a temporary basis with a different cable to prove it’s not anything else? If not, then all you can really do before asking whoever you paid to do the job to re-check the work is swap the patch cables out. Obviously it’ll be under warranty with whichever company did it, just agro and an extra visit that’s not exactly ideal in current times.