79. About Network Interface MAC Addresses
Every adapter (wired or wireless) has a unique hardware address burned onto a ROM (Read Only Memory) chip by the adapter's manufacturer. This unique address is called the MAC (Media Access Control) hardware address. These unique addresses are actually used by computer and networking hardware to send data between devices on a network.
MAC (Media Access Control) hardware address A 48-bit hexadecimal number burned onto a ROM chip on a network adapter (for a computer on the network) or network interface card (for a router). MAC hardware addresses (also sometimes referred to as physical addresses) are used by computers and other network devices to ensure that the bit stream of data moving on the network medium is correctly identified in terms of source and destination.
You are probably thinking that IP addresses, not MAC addresses, provide the addressing system for the network. IP addresses do provide the addressing system for TCP/IP networks. However, for two devices, such as computers outfitted with network adapters, to complete a data transaction (or data transfer, if you prefer), the IP address is actually resolved to the MAC hardware address on the computer's network adapter. This process ensures that the data is transferred to the correct network device because the MAC address is truly unique for each device. Here's an example of a MAC hardware address: 00-50-56-C0-00-1.
Most WiFi routers list the currently connected computers and their MAC hardware addresses on the attached devices or similarly named screen, which makes it easy to add these computers to a MAC access list. The MAC access list is typically found in the router's configuration pages by clicking the Wireless Card Access Setup or similar command.
If a connected computer appears on the attached devices screen, you can actually cut and paste the MAC address you want to create to the MAC access list, although you will have to move from the connected devices list to the MAC access list using the appropriate router command (typically found on the left side of the web pages used to configure and monitor the router). Oddly enough, you might find that a connected computer is not listed by the router, even though you know that the computer is connected. In this case, you need to view the MAC address on the computer and then type it into the router's MAC access list manually.
To view the MAC hardware address for a computer's network adapter, click the Start button and then click the Run command. In the Run dialog box, type command and press Enter. A command prompt window opens. Type the command ipconfig/all and press Enter. The IP address and subnet mask for the adapter is listed, as is the physical address (the MAC hardware address) for the adapter. When you enter the MAC hardware address in the MAC access list, you will also need the name of the computer (the host name). The host name is listed along with the IP information and the MAC address when you run the ipconfig/all command.
The conversion of IP addresses to MAC addresses and vice versa is something that happens completely transparently when data moves on the network. However, because MAC addresses are completely unique, you can actually use them as another way to make your WiFi network more secure. You can create a MAC access list on your WiFi router. This access list is composed of the MAC addresses from the computers you want to be able to connect to your WiFi network. Although MAC access lists are not a fool-proof system for protecting the WiFi network, they do negate the intrusion of "less-dedicated" hackers.
Securing a network (even a home WiFi network) requires you to take advantage of all the possibilities for keeping your network data private. This means that you should throw pretty much every security strategy at the network, hoping that it will be enough to keep out hackers who seem determined to break into even small networks. Using a MAC access list to "lock out" computers not included on the list is just another security strategy you might want to take advantage of. Because hackers seem to never sleep (or bathe), they can quickly find holes in almost any new strategy for securing a network.