So I thought I understood networking better than I apparently do... can someone explain this to me:
We have a machine with an NTRON 700 switch and star topology. Connected to this switch are an AB CompactLogix PLC, several remote IO blocks, an HMI, and several servo drives (Kinetix).
All devices are using IP addresses of the form 10.107.8.XXX
The subnet on the PLC, the HMI and one of the remote IO blocks uses a 255.255.0.0 subnet. The subnet on the servos and remaining remote IO is 255.255.255.0
In RSLinx I can only 'see' and configure the devices on the same subnet as my laptop's NIC card (so depending on which subnet I have my NIC set to, I only get half the devices). Yet, when I connect to the PLC and go online with it the PLC is having no issues communicating with all devices and the machine seems to be running fine.
How is this??? My expectation would be that the PLC (with subnet 255.255.0.0) would not be able to see or communicate with any of the devices on the 255.255.255.0 subnet (just as RSLinx on my PC cannot when I am set to a 255.255.0.0 subnet). Obviously this is not the case, but I'm having a hard time understanding why. My only guess is it has to do with the Layer-2 vs. Layer-3 (MAC vs. IP) nature of the connection through the switch, but I'm having a hard time understanding the specifics of what is going on...
Enlighten me!
Thank you
-Z
We have a machine with an NTRON 700 switch and star topology. Connected to this switch are an AB CompactLogix PLC, several remote IO blocks, an HMI, and several servo drives (Kinetix).
All devices are using IP addresses of the form 10.107.8.XXX
The subnet on the PLC, the HMI and one of the remote IO blocks uses a 255.255.0.0 subnet. The subnet on the servos and remaining remote IO is 255.255.255.0
In RSLinx I can only 'see' and configure the devices on the same subnet as my laptop's NIC card (so depending on which subnet I have my NIC set to, I only get half the devices). Yet, when I connect to the PLC and go online with it the PLC is having no issues communicating with all devices and the machine seems to be running fine.
How is this??? My expectation would be that the PLC (with subnet 255.255.0.0) would not be able to see or communicate with any of the devices on the 255.255.255.0 subnet (just as RSLinx on my PC cannot when I am set to a 255.255.0.0 subnet). Obviously this is not the case, but I'm having a hard time understanding why. My only guess is it has to do with the Layer-2 vs. Layer-3 (MAC vs. IP) nature of the connection through the switch, but I'm having a hard time understanding the specifics of what is going on...
Enlighten me!
Thank you
-Z