A MAC address is a permanent physical identifier assigned to a network interface card (NIC), while a logical address, such as an IP address, is a dynamically assigned identifier used by network protocols like TCP/IP. Together, they allow routers and switches to effectively deliver data packets across local area networks and the global Internet.

Physical MAC Addresses

The chances are very good that you'll never see the MAC address for any of your equipment because the software that helps your computer communicate with a network takes care of matching the MAC address to a logical address. The logical address is what the network uses to pass information along to your computer.

If you'd like to see the MAC address and logical address used by the Internet Protocol (IP) for your Windows computer, you can run a small program that Microsoft provides. Go to the "Start" menu, click on "Run," and in the window that appears, type WINIPCFG (IPCONFIG/ALL for modern Windows versions like Windows 10 or Windows 11). When the gray window appears, click on "More Info" and you'll get this sort of information:

Windows IP Configuration:

Host Name: lasmallnetworks
DNS Servers: 208.153.64.20
Node Type: Broadcast
IP Routing Enabled: Yes
WINS Proxy Enabled: No
NetBIOS Resolution Uses DNS: No
      

Ethernet adapter:

Description: PPP Adapter
Physical Address: 44-45-53-54-12-34
DHCP Enabled: Yes
IP Address: 227.78.86.288
Subnet Mask: 255.255.255.0
Default Gateway: 227.78.86.288
DHCP Server: 255.255.255.255
      

There's a lot of information here that will vary depending on exactly how your connection to the Internet is established, but the physical address is the MAC address of the adapter queried by the program. The IP address is the logical address assigned to your connection by your ISP or network administrator. You'll see the addresses of other servers, including the DNS servers that keep track of all the names of Internet sites (so you can type "www.lasmallnetworks.com" rather than "216.27.61.189") and the gateway server that you connect to in order to reach the Internet. When you've finished looking at the information, click OK. (Note: For security reasons, some of the information about this connection to the Internet has been changed. You should be very careful about giving your computer's information to other people -- with your address and the right tools, an unscrupulous person could, in some circumstances, gain access to your personal information and control your system through a "Trojan Horse" program.)

Network Logical Addresses

Every piece of equipment that connects to a network, whether an office network or the Internet, has a physical address. This is an address that's unique to the piece of equipment that's actually attached to the network cable. For example, if your desktop computer has a network interface card (NIC) in it, the NIC has a physical address permanently stored in a special memory location. This physical address, which is also called the MAC address (for Media Access Control) has two parts, each 3 bytes long. The first 3 bytes identify the company that made the NIC. The second 3 bytes are the serial number of the NIC itself.

The interesting thing is that your computer can have several logical addresses at the same time. Of course, you're used to having several "logical addresses" bring messages to one physical address. Your mailing address, telephone number (or numbers) and home e-mail address all work to bring messages to you when you're in your house. They are simply used for different types of messages -- different networks, so to speak.

Logical addresses for computer networks work in exactly the same way. You may be using the addressing schemes, or protocols, from several different types of networks simultaneously. If you're connected to the Internet (and if you're reading this, you probably are), then you have an address that's part of the TCP/IP network protocol. If you also have a small network set up to exchange files between several family computers, then you may also be using the Microsoft NetBEUI protocol. If you connect to your company's network from home, then your computer may have an address that follows Novell's IPX/SPX protocol. All of these can coexist on your computer. Since the driver software that allows your computer to communicate with each network uses resources like memory and CPU time, you don't want to load protocols you won't need, but there's no problem with having all the protocols your work requires running at the same time.

Frequently Asked Questions

Conclusion

In summary, understanding both physical MAC addresses and logical network addresses is essential for grasping how data moves across complex networks and the Internet. By combining physical hardware addresses with logical protocols, routers and switches are able to efficiently deliver massive amounts of traffic seamlessly worldwide.