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I have a Windows 11 PC A connected to an Ethernet switch. Also connected to the switch is a CAN-bus-to-Ethernet bridge. PC A sends and receives TCP packets (mostly) successfully to the CAN-Ethernet bridge.

For some reason I don't understand I can't run npcap on computer A so I have also connected two other computers B and C to the same Ethernet switch both running Wireshark.

I can ping the CAN-Ethernet bridge form PCs B and C. But why can't I see any TCP packets going between PC A and the CAN-Ethernet bridge?

If I ping the CAN-Ethernet bridge, I can see the pings in Wireshark but only on the laptop doing the pinging. I don't seem to be able to capture any packets going between PC A and the CAN-Ethernet bridge (although they are communicating with each other) with WireShark on computers B or C.

If, however, I run the application on PC B or C as well as WireShark, then that computer can see the traffic between the application and the CAN-Ethernet bridge.

What do I have to do to be able to able to see the TCP packets on a computer which isn't communicating with the CAN-Ethernet bridge?

I have a Windows 11 PC A connected to an Ethernet switch. Also connected to the switch is a CAN-bus-to-Ethernet bridge. PC A sends and receives TCP packets (mostly) successfully to the CAN-Ethernet bridge.

For some reason I don't understand I can't run npcap on computer A so I have also connected two other computers B and C to the same Ethernet switch both running Wireshark.

(not sure if this image shows correctly - If not, it can be seen at: https://www.dropbox.com/s/u37fkamoh87bkbn/Connection%20-%20cant%20see%20data.png?dl=0).

I can ping the CAN-Ethernet bridge form PCs B and C. But why can't I see any TCP packets going between PC A and the CAN-Ethernet bridge?

If I ping the CAN-Ethernet bridge, I can see the pings in Wireshark but only on the laptop doing the pinging. I don't seem to be able to capture any packets going between PC A and the CAN-Ethernet bridge (although they are communicating with each other) with WireShark on computers B or C.

If, however, I run the application on PC B or C as well as WireShark, then that computer can see the traffic between the application and the CAN-Ethernet bridge.

What do I have to do to be able to able to see the TCP packets on a computer which isn't communicating with the CAN-Ethernet bridge?

I have a Windows 11 PC A connected to an Ethernet switch. Also connected to the switch is a CAN-bus-to-Ethernet bridge. PC A sends and receives TCP packets (mostly) successfully to the CAN-Ethernet bridge.

For some reason I don't understand I can't run npcap on computer A so I have also connected two other computers B and C to the same Ethernet switch both running Wireshark.

(not sure if this image shows correctly - If not, it can be seen at: https://www.dropbox.com/s/u37fkamoh87bkbn/Connection%20-%20cant%20see%20data.png?dl=0).

I can ping the CAN-Ethernet bridge form PCs B and C. But why can't I see any TCP packets going between PC A and the CAN-Ethernet bridge?

If I ping the CAN-Ethernet bridge, I can see the pings in Wireshark but only on the laptop doing the pinging. I don't seem to be able to capture any packets going between PC A and the CAN-Ethernet bridge (although they are communicating with each other) with WireShark on computers B or C.

If, however, I run the application on PC B or C as well as WireShark, then that computer can see the traffic between the application and the CAN-Ethernet bridge.

What do I have to do to be able to able to see the TCP packets on a computer which isn't communicating with the CAN-Ethernet bridge?

Thanks.