When configuring your router, you'll often see something called a MAC address. This may happen when you go to a status page that shows the computers that are connected to the router. You'll also run across it on a wireless security settings page. What exactly is a MAC address? I'll try to explain it without getting too technical.
A MAC address is usually represented as a string of hexadecimal numbers that looks something like this 00:14:38:44:A7:4A. The colons really don't mean anything and just make it easier to read.
A hexadecimal number is nothing special. If you are not familiar with the term, basically it's just a regular number, but represented in a different counting system (base 16), rather than the counting system that humans are used to (base 10). Base 16 just means that one digit can represent 16 unique values (0-15), rather than (0-9) which we are all used to. Computers use binary (base 2), and everything to a computer is either 1, or 0. So hexadecimal is used as a shorthand to represent binary numbers. There is more to that, but for now, that's all you really need to know about hexadecimal.
Basically, when manufacturers physically create a network card, whether it's a wireless network card, or a regular wired network card, they stamp a serial number on the card. This number is a unique identifier, which means no other network card, whether created in the present, in the past, or in the future will have that same exact number. Because this number is unique, devices created by different manufacturers can be trusted to work together. Your home router depends heavily on this number to reliably communicate with the different computers plugged into the router. For example, if you have several computers in your home connected to a router, you typically share an Internet connection that is managed by the router. When you surf the web, data passes to the router which then routes it out to your cable modem or DSL modem, and then out to the Internet. Web pages that you see are transmitted back along that same path in reverse order. For your router to know which computer to send that data to, on a hardware level, it relies on the MAC address to figure out which computer in your home receives the data.
If MAC addresses were not guaranteed to be unique, this whole process would not work. For example, if two computer plugged into a router had the same MAC address, the router would be confused as to which computer to send the data to. There would be a conflict. It would be as if two houses on your street had the same address. When the mailman comes, he wouldn't know which letters to send to which house.
MAC Address Filtering
Most home wireless routers have an option for MAC Address Filtering. This is a security measure which tells the router to only communicate with MAC addresses that match exactly to it's list of trusted MAC addresses. You would enter the MAC address of the wireless cards that people in your home have. Anyone who is not on this list will not be able to access your network or surf the web. Remember, this is not on a per computer basis, it's on a per network card basis. So, if for example, you have a USB wireless network card, or a PC Card type network card that was on the trusted MAC address list of the router, then if you attach that card to a different computer, that new computer would be allowed access, because the MAC address would match.
What is my MAC Address?
In Windows, to find out your MAC address you could open a command prompt by going to the start menu and selecting "Run". In the dialog box type "cmd.exe". You should see a command prompt. Now type "ipconfig /all". A list of network cards attached to your computer will appear and you'll see the MAC addresses along with other information like IP addresses, for each one.
Can I Change My MAC Address?
In most cases you can. If you go to Control Panel/Network Connections, you'll see a bunch of network adapters. Right click the one you want and select "Properties". Then press the "Configure" button and choose the "Advanced" tab. You'll probably see an item called "Network Address" or something like that, where you can select and enter a new MAC address. It's not guaranteed but most network cards these days have this capability.
It's not advisable to change your MAC address. Like I stated before, if two devices have the same address, things will not work right or the network. So, you better know what you are doing if you want to mess around with this. Practically speaking, as long as you choose a new MAC address that is not identical to any others on your network, you should be fine.
So, for a general overview that's basically it about MAC addresses. Their are other interesting things about MAC addresses like you can figure out who the manufacturer of the network card is by looking at certain digits in the MAC address. Anyway, if you can understand some of the concepts I've explained here, it'll help you understand a little bit more about how networking works.
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