Multicast messages

Ewon Support eWON Cosy
#1

Hi,

I am trying to connect to a network of PLCs through a new Cosy 131. Initial set-up worked without any issues. I can ping all my devices remotely, and I can get full access to most devices, like our ABB VFD.

The issue comes with accessing the PLCs. These communicate with Multicast messages. I have attached a screenshot of a typical Wireshark capture on the LAN side. These messages are not visible when capturing data on the device running eCatcher (on its TAP interface). I have tried turning on the BroadcastForwarder option on my Cosy. This did seem to do something, because my data usage rate went up, but I still didn’t see anything on my client side.

Do you have any advice on how to get this working?

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#2

Hi @BasZF,

Sorry for the delay. We had a number of posts get lost and just discovered them. For quicker responses in the future, please create a case at support.hms-networks.com.

As for your question, it is a rule of TCP/IP Networking that broadcast messages are not forwarded to other networks. They are only used inside of the local subnet.

Our workaround allows the Ewon for forward broadcasts over the VPN, but whether or not it will work depends on the application. By default it is disabled because it can lead to excessive traffic over the WAN and VPN networks. It sounds like you have already tried this?

(System > Setup > Storage > Edit com cfg) and change BroadcastForwarder value from 0 to 1.

In this case, you will probably have to talk to the PLC manufacturer engineers to find out exactly how the application works and why the forwarded broadcast messages aren’t working. They should be able to figure this out from the pcaps your have taken with Wireshark.

Please let me know if you have any other questions.

Best Regards,

Kyle Reynolds