George_J (Customer) asked a question.
Stride IO module doesn't respond to ARP requests.
I discovered that a Stride IO module fails to respond to ARP messages under certain conditions. When my PC sends ARP requests for the Stride IO module, the module responds as expected.
When my controller sends ARP requests, there is no response from the Stride IO module. The difference is that my controller sends 18 null bytes after the ARP request. The controller is using the LWIP protocol stack. My controller module is a SIO-MB16CDD2.
Is there a firmware patch available for this issue?
Requesting Wireshark captures of both the PC’s ARP request to the Field I/O module as well as the a capture of the Controller’s ARP request to the module?
https://support.automationdirect.com/docs/an-misc-033.pdf
Gateway is 192.169.0.1 (none present)
Stride IO is at 192.168.0.100
Controller is at 192.168.0.10
Netmask is 255.255.255.0
ARP requests to Stride IO are at lines 7 (PC) and 47 (Controller)
George Johnston
Sr. Firmware Engineer
[cid:image001.png@01D399F1.BA75D990]<http://www.espsafetyinc.com/>
In addition to the Wireshark captures, can the you provide the following:
Wireshark screen captures and net address info were sent by email
Which email?
Please PM me the files and I will get them to the appropriate team for review.
After reviewing the capture it appears there is no problem with the Stride IO device.
First the Wireshark capture is being done on the dell PC.
The evidence of this is that the outgoing “Dell PC” ARP request is 42 bytes. The 18 padding bytes are added by the network adapter after the outbound packet has gone past npcap. If you were to use a managed switch with port mirroring, you would see the full 60 bytes in the outgoing ARP request.
Second, given that the Wireshark capture is on the dell PC, the PC will not see the ARP response from the Stride IO because it is a directed response (not broadcast) and the switch will only forward it back to the port where the STM device on 192.168.0.10 resides. The switch will not forward it to the port where the dell PC resides and so it will accordingly not show up in your capture. Again, if using a managed switch with port mirroring and capture the mirror data, you would see the Stride IO ARP response as expected.
Not using a managed switch is misleading by seeing the STM device ARP request (broadcast) at the dell PC network adapter due to the switch forwarding broadcast to all ports.
I accept your analysis. I am using an unmanaged hub. So the Stride IO ARP reply to my controller isn't visible in the Wireshark capture. I have verified that the Stride IO module is responding to my controller's ARP request as designed. I was not aware that Wireshark would not show the correct frame size for the PC host running Wireshark. Lesson learned.
Thank you for clarifying a confusing set of symptoms. As a newbie to low level Ethernet debugging, your input was very valuable. George