Why does my network speed nosedive when using a gigabit switch?

[Combat squirrel]

As title, I need a switch upstairs to route some cables - however iv tried 3 different ones now (granted they are several years old but still a gigabit switch! - a netgear one and TP links) - but when using them the speed drops to 10mb speeds - its connected by a network cable to an Asus RT-AX92U router.

Obviously this isn't a useable speed - however if I connect my PC to this cable, I instantly get maxed out 1000mb (gigabit) network speeds with no issues.

What's going on here? Do I simply need a new / modern switch ?

 

[JohnStewart]

I've got a similar set-up in my house, with my Asus router connected to the Openreach ONT, and then one of the LAN ports going to a gigabit switch in the loft (Cat 6a cable run up the inside of the walls). From there I run cat 6a cables to several rooms. All the ethernet ports on faceplates give a gigabit connection straight away. I'm just using a cheap 8 port Netgear switch that I bought about 6 years ago from Amazon on a black Friday deal - I think it was £15.

Your Asus router has gigabit LAN ports and as you say, connecting your PC directly to the router using this cable gives full speed, so that's not theissue. This leaves either the switch or the cables as a possible culprit. As you have tried several gigabit switches, that should in theory rule out the switch as being the problem.

Generally, the ports on the switch should auto negotiate the maximum speed supported by the device connected to it and the cable, unless it's been configured (if it's a managed switch) to use a certain speed.

Can you try connecting your PC to the switch via a different ethernet cable if you have a few to choose from, and maybe try swapping the cables around and trying all the ports of the switch to see if anything makes any difference?

 

[WJA96]

Just to be clear - you have a long cable going from one room to another?

Router->long cable->gigabit switch->PC = 10Mbps connection at PC

Router->long cable->PC = 1000Mbps connection at PC

Is that correct? If so there must be a second network cable between the gigabit switch and the PC. Have you tried replacing that cable?

If so, do you have more than one cable plugged into the switch that goes back to the router (packet storm?)

 

[Combat squirrel]

Thanks all - as WJA says, this is the issue:

Router->long cable->gigabit switch->PC = 10Mbps connection at PC

Router->long cable->PC = 1000Mbps connection at PC

I have connected the cable that was going from pc to gigabit switch DIRECTLY TO the long cable (simply coupled the cables together) and that also works 100% fine at 1gb network, no issue.

Simply adding in any gigabit switch I have into the line ruins it I can't find out why, I guess I could buy a newer switch but its a weird one, my Asus RT-AX92U router is fine as far as I know.

EDIT: Now for some reason its connecting for about 2 mins say, then the connection drops then it reconnects again, all at 1gb but it only seems to stay connected for a couple mins, drops the connection, reconnects again - tried both the Mac mini built in ethernet port and also my call digit ethernet port (tb 3 adaptor), but.....as I write this and I keep an eye on the connection it appears to have stabilised now and isn't disconnecting anymore.....how strange.

 

[pp111]

I don't know a thing about older switches, in fact I don't know much about new ones (!), but I am wondering if this has something to do with power saving on the ethernet?

 

[Nikumba]

Try forcing your PC network port to 1Gb rather than auto-negoitate, just in case the switch is doing something funny.

Do you get 10mb speeds regardless of which port on the switch your pc is plugged into?

 

[WJA96]

I don’t know if you’ve read any reviews of your router but packet loss on Ethernet seems to be a recurring issue. If the packet loss is very high it might cause the connected device to drop down to a slower speed.

 

[bledd]

Do you have a cable tester?

 

[~cw]

Chances are you've enabled features which require the CPU to handle all packets, thus losing the benefit of hardware/NAT acceleration.

Check QoS is not enabled, likewise other 'features' like SPI, firewall, time of day access, any AiMesh, AiProtection or TrendMicro stuff, etc.

Try rolling back firmware if you can...

 

[WJA96]

Chances are you've enabled features which require the CPU to handle all packets, thus losing the benefit of hardware/NAT acceleration.

Check QoS is not enabled, likewise other 'features' like SPI, firewall, time of day access, any AiMesh, AiProtection or TrendMicro stuff, etc.

Try rolling back firmware if you can...

As I understand it if the OP connects the client directly to the router there is no drop in speed. It only drops in speed when connected through a gigabit switch. I believe the OP has tested 2 switches and both gave the same slowdown effect. So I don't see how any of the router controls could have an effect.

 

[~cw]

As I understand it if the OP connects the client directly to the router there is no drop in speed. It only drops in speed when connected through a gigabit switch. I believe the OP has tested 2 switches and both gave the same slowdown effect. So I don't see how any of the router controls could have an effect.

Gah sorry I missed that. My addled brain read 'switch' as the internal switch of the router. FCS errors are corruption during transit, so odds are it's an electrical fault.

1. First suggestion would be that the switch is goosed - but OP's tried multiple switches. So my first suggestion is to get another ethernet cable and properly electrically test the one you're using
2. Second suggestion is that the ethernet's termination is selectively shoddy, and/or the socket on the switches are not tensioned enough to make a good contact. Or one/more of the terminations are failing when the cable is held at an angle versus a different angle when terminated into the PC directly
3. Third suggestion is that there's a kink or damage to the insulation (it happens) or some RF bleeding into the pairs causing the slowdown. Echo the sentiments of someone else saying "get a cable tester". Spotting dodgy pairs can be a nightmare
4. Fourth suggestion is that the port on the Asus router is similarly dodgy, in which case try a different port. Maybe something really obscure like marginal voltage output, which the PC NIC is more tolerant to than the intermediate switch - could end up reducing the far end machine to a painfully slow speed due to line errors.

If it's the Asus router that would be particularly cruel. Some Intel NICs can perform cable quality assessments through the PROSet software, give that a try. And a good excuse to buy a spare Prosafe GS108, £30, useful for for the toolbox/testing.


When going via the intermediate switch, run a file transfer to saturate the link, open a Powershell command prompt and use netstat -e (or netstat -s) to view summary statistics. To view frame errors, in Powershell enter Get-WmiObject Win32_PerfFormattedData_Tcpip_Networkinterface | Select Name, PacketsReceivedErrors, PacketsOutboundErrors and periodically re-run it to see if the count increments significantly.