That's more information than I've been able to find in any documentation on the AB web site. I did find a paragraph on ARP in the RSNetworks for EtherNet/IP manual, but it is vague, and I don't completly understand ARP. I was hoping the solution might be universal so that at least all the devices could be seen on the wire. From what I have been to figure out (never heard of ARP before last week Friday), a gratuitous ARP message would be enough to at least see what IP addresses are in use, which would be a good first step toward a network who, but my understanding is that there is no ARP service that says "anyone out there start talking". It's all based on timeouts or device power-up only.
I'd like to get me hands on some demo software and use a packet sniffer to watch what is going on with some of these packages.
Do you know what Sixnet, Wago, Opto, or any other manufactures do? Do you have any example documentation on the use of the ports you talk of?