Mac – create an Ethernet network without using IP

ethernetmac addressnetworking

As I understand from the ISO-OSI model, MAC addresses operate on a different layer than IP addresses. This is clear to me.

I can accept that Ethernet (LAN) just does not make use of IP addresses to do communication, but uses MAC addresses. I understand that these MAC addresses cannot be used for routing outside of a LAN, as they are not hierarchically defined. I also understand that IP is the best way to do routing over the big Internet. What I am not entirely convinced of, is that MAC addresses are the best way to communicate in a LAN

My questions are the following:

  1. Couldn't Ethernet make use of IP addresses to send messages? I'm not saying it should, I'm just asking if it could have chosen to do so.
  2. As Ethernet uses MAC addresses for communication, could I create an Ethernet network where devices would not have an IP address, just a MAC address?

Best Answer

Could Ethernet have used IP addresses instead of it's own data-link-layer addresses? Certainly not, if it wanted to be agnostic about what layer-3 protocol it used.

We design networking protocols in layers so that we can mix-and-match layers.

Ethernet was originally developed by Bob Metcalfe et alia at Xerox PARC to be Network-layer agnostic, because their goal wasn't just TCP/IP access but also for Xerox's own proprietary XNS network protocol stack/suite.

DEC (Digital Equipment Corporation) became another early adopter, using it primarily for their DECnet protocol stack/suite.

In the late 80's and early 90's there were lots of competing LAN protocol suites (all completely independent of TCP/IP) running on corporate Ethernet LANs. Besides XNS and DECnet, there was Apple's AppleTalk (EtherTalk), Novell's IPX, Banyan VINES, NetBEUI, DLC/LLC, IBM SNA, OSI/ISO, and others I've forgotten.

So, Yes, you can use Ethernet without IP. Lots of corporate networks did it in the 80's and 90's.

Because Ethernet was designed to not care about what Layer-3 (Network Layer) protocol was running on it, it was relatively easy for those corporate LANs to support mixes of various vendors' equipment, and it was relatively easy for those LANs to add IPv4 support when the Internet took off in the mid to late 90's, and it has been relatively easy for us to add IPv6 support now.