Windows cannot communicate with PLC using Internal Connection - APC910 Hypervisor

Hi everyone,

Unless I physically connect ETH1 to ETH2 via an ethernet cable, I am unable to ping or communicate with the PLC on my APC910…

I have an APC910, I have configured the system so that ETH1 is GPOS, and ETH2 is ARemb. There is also a 3rd internal connection. This 3rd connection appears in the Network as “Real-Time Hypervisor PCI Network Adapter” and shows it is connected, but I cannot open my mappview or ping the PLC.

It is only working properly when I connect ETH1 to ETH2 with an ethernet cable.

What setting could I have possibly overlooked for the internal adapter? I have tried with DHCP and a static IP, just as I have experimented with the physical ETH1/2.

Thanks and please let me know what you think!

Hi Adam,

Welcome to the Community!

I want to make sure I understand you correctly.

  • When you try to access mappView normally, are you using the internal Ethernet address?
  • When you connect the two ports physically together, are you then using the Eth2 IP address to access mappView?

Even though the PC has two physical ports, there actually four IP addresses to be aware of:

  • Eth 1 - GPOS - IP set in Windows
  • Eth2 - AR - IP set in Automation Studio (or by DHCP server)
  • EthInternal - AR is a DHCP server - Default IP is 192.168.137.1 - assigns Windows an IP (default 192.168.137.2 to 192.168.137.5)

Both sides of the EthInternal network need to be on the same subnet in order for Windows to talk to AR. However, the two physical Ethernet ports should be on a different subnet (and a different one from each other). Using the same subnet for multiple interfaces can cause communication problems. If you’re able to connect the two physical ports with an Ethernet cable and use them to communicate, it sounds like they’re probably on the same subnet so I recommend changing this first.

Another thing to check is to verify that you’ve installed both of the required drivers in Windows (the Hypervisor driver and the ADI driver). I’ve seen network connectivity issues happen if one of those is not installed.

Thank you for the quick reply.

After looking at the ports once more, I changed the ETHinternal to the default 192.168.137.1, and the windows internal IP to 192.168.137.2. At the same time I was able to connect with my Laptop ethernet port to the physical port and also view the mappview.

There is an interest in my organization to use the same subnet for all ports so that it is possible to connect to mappview using a single IP address whether on the GPOS or connected to the physical ETH port. Based on your last response, it seems it is frowned up to do this? What type of communication problems could we encounter?

Update: AS prevents me from even trying to use the same subnet.

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No problem! I’m glad it’s working now.

I’m definitely not a networking expert, but my understanding is that using the same subnet for multiple separate Ethernet interfaces on the same device causes traffic to get lost. The operating system distinguishes the interfaces using their IP addresses. Packets bound for subnet A go to interface A and packets bound for subnet B go to interface B. Presumably, subnets A and B have different devices that are being communicated with. If you use the same IP address for interfaces A and B, there’s no guarantee that packets bound for device A will not end up on interface B and vice-versa. This also means that when your PC receives data on an interface, it may not be sure which process needs that data.

Because Windows and AR are two separate operating systems, it may be the case that you can use the same subnet for both physical interfaces. One interface will always go to Windows and one will always go to ARemb. However, I would still avoid this because it can be confusing given that different interfaces on a device usually use different subnets.

If you want to easily find the APC (and get to mappView) regardless of IP, then a good solution is to use the Hostname instead. The hostname is also set in the Ethernet configuration and the default is “br-automation”. You can change this to, say, “my-apc910”. Then, to access mappView, you just go to a browser and type “http://my-apc910:81”. You don’t need to remember the IP address in this case. Just remember that you can’t have multiple devices with the same hostname on the same network or else the router won’t know which device the traffic should go to.

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