Networked device doesn't work with certain switches

1

I have a networked device (an old motion controller) that I have connected to my network via a switch. My PC is connected to the same switch. This configuration works as expected and I can ping and open TCP connections to the motion controller.

However, if I swap the switch with some other models then I can no longer ping/access the device. I've tried two other (otherwise working) switches and the device doesn't work with either. Generally speaking isn't a switch just a switch? What differences can I look for between the switches to troubleshoot this?

The switches I've tried (all gigabit) are:

Working:
  D-Link DGS-1008D 
  TP-Link TL-SG1008D 

Not working:
  TP-Link TL-SG1016D 
  HP ProCurve 2708 J4898A

101

Posted 2015-08-26T00:12:40.123

Reputation: 113

what is the device in question? – pete – 2015-08-26T01:36:28.543

This piece of... @pete. – 101 – 2015-08-26T01:44:08.407

do you have a simple hub you can place between the motion controller and the switch(es)? this would allow you capture packets, and also determine if there isn't some form of hardware incompatibility (eg, power-over-ethernet; energy-efficient-eth, etc...) – pete – 2015-08-26T02:05:48.890

possibly a helpful note for other readers, the controller uses modbus/TCP; i'm quite unfamiliar, but i did see one mention of occasional network issues involving message timing. – pete – 2015-08-26T02:14:40.247

Unfortunately not @pete. I might have a look with wireshark... – 101 – 2015-08-26T02:27:12.623

Yes it does use Modbus, but even pinging the device is not possible on the "bad" switches @pete. – 101 – 2015-08-26T02:32:19.190

Let us continue this discussion in chat.

– pete – 2015-08-26T02:41:50.957

Answers

3

The most likely difference is speed and duplex negotiation. You might find the device is acting as 10 megabits half duplex and your gigabit switches can't handle this.

(Your switches rule out the possibilities of it being a VLAN issue or PoE issue)

davidgo

Posted 2015-08-26T00:12:40.123

Reputation: 49 152

Thanks, I know the device certainly doesn't connect at gigabit speeds, so that could well be it. Is there a way to check that from a PC if the switches are unmanaged? – 101 – 2015-08-26T02:36:46.820

Not really, but - based on the specs you provided - your switches are all unmanaged. – davidgo – 2015-08-26T02:43:13.953

Asked: 2015-08-26T00:12:40.123

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Active: 2015-08-26T02:34:53.133