Case 1 – Accessing data inside an Allen- Bradley PLC¶
In this case, a ControlLogix uses the ENET bridge in slot 1 (0 based counting) for communicating with the CIP client. The processor module itself is in slot 2. An additional ControlNet Bridge is in slot 4 and is not used in this scenario.
The MindConnect sends a request to the ControlLogix on 192.168.0.22, slot 2.
This communication path (route parameters) is formed as follows:
It recognizes the CIP message is not for it and therefore, it removes its address part (1) from the CIP message. The remaining CIP message is being forwarded to the processor module as indicated by the remaining address information (2). The message contains a reduced communication path with the slot number. The processor removes that information and start interpreting the remaining message, as there is no further routing information in the packet.
The following Wireshark packet analysis shows the additional segment.
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