Hypothetically if I wanted to make a custom point to point protocol that uses Ethernet, can I use Ethernet in such a way where the two devices communicate with each other by broadcasting their messages? I know that in practice you would always use IP addresses and ports but the question is purely academic.

  • Possible, yes. Reasonable, no. Broadcasting is inefficient and Ethernet is rather hard to tap into for an application-layer protocol on most current platforms. You'd be much better off using decent IP addressing and UDP in the transport layer.
    – Zac67
    Apr 19, 2022 at 11:50
  • 1
    Perhaps if you describe in a little more detail what you're trying to accomplish, we might be able to suggest a better way,.
    – Ron Trunk
    Apr 19, 2022 at 12:09
  • @RonTrunk I've seen many devices like PLCs using Ethernet for a point to point connection. You don't need to set up an IP address. You plug in the cable and you are good to go. I was wondering how did this solution approach the fact that it does not know the endpont's IP address. I reasoned that one approach would be using custom layer 2 protocol for IP identification and the other would be using broadcast. I just wanted to know if the latter was even possible, however as Zac67 mentioned it wouldn't be practical.
    – Phill Donn
    Apr 19, 2022 at 20:40
  • Ethernet uses a different address scheme (MAC addresses). It has nothing to do with IP addresses. On a single network , you don’t need IP.
    – Ron Trunk
    Apr 19, 2022 at 21:23
  • In other words, PLCs use MAC addresses, not IP addresses.
    – Ron Trunk
    Apr 19, 2022 at 21:40


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