Good morning Sandeep,

Thank you very much for your question. The path you provided is unsupported, and I'd be quite interested to know if it actually does anything?

The reason is, the IP address used is not officially supported by Rockwell devices as the IP Address is not a valid Device address.

For others who are viewing this, let me start by pointing out what is shown in the 4 minute mark in the lesson – it shows the help file for the MSG which details how the path alternates between Port and Node_Address.

So in your example, that would be:
– Port: 2
– Address: 255.255.255.0
– Port: 1
– Address: 0

The first Port is dependent on your hardware. For instance, if your MSG was in an 1756-L63*, then port 2 would be the serial port.

* Without the catalog number of the Controller that has the MSG in it, you cannot know what Port 2 is because you don't know what physical ports your controller has (not all controllers have the same ports)

The next number is the Node_Address, and I can confirm 255.255.255.0 is not a valid IP address and not officially supported by Rockwell (see below for more info.)

If I had to guess I would say someone accidentally entered the Subnet Mask incorrectly as the IP address.

The next number is Port 1, which always represents the target device's backplane.

And finally you have Address 0, which is likely referring to Slot Zero, but to know exactly what it represents requires knowing the exact catalog number of the destination device.

That said, I want to return to your 255.255.255.0 IP address of your messages target.

You will not find this as a supported Destination address in the A-B Ethernet Module manual. Some of the reasons include:
– Addresses ending in 0 (zero) represent the entire network, and therefore are not officially supported with the MSG instruction
– Addresses ending in 255 are a broadcast address, and therefore are not officially supported with the MSG instruction
– IP address 255.255.255.255. It is the broadcast address of the zero network or 0.0.0.0 (aka this network) and as such is not officially supported with the MSG instruction
– Officially, the only supported IPv4 Private Address Ranges are 10.x. x.x/8, 172.16. x.x/12, and 192.168. x.x/16 (and not 255.x.x.x.) Put another way, these are the only ranges professionals should assign to devices inside their plants.

To read more about this, check out the below articles:
– https://searchnetworking.techtarget.com/answer/Can-you-assign-an-IP-address-ending-in-0-or-255
– https://en.wikipedia.org/wiki/Broadcast_address

Hope this helps,

Shawn Tierney,
Instructor at The Automation School