What Are Mac Addresses?

[PathofNeo 0]

I'm feeling a bit dumb here, but could someone explain to me exactly what a MAC address is and what it does? Is it broadcast like an IP? Who can find out my MAC address? Why would they want my MAC address? Etc. Any help here would be great. Thanks.

Edited June 16, 2005 by microscopic^earthling (see edit history)

[miCRoSCoPiC^eaRthLinG 0]

MAC (Media Access Control) address is the physical address of the network card installed on your system - with which you connect to your router/modem over UTP ethernet cable. Network adapter cards use a burned-in address - this unique hardware address burned into a ROM chip on that network interface card.

 

This hardware address on the network interface card provides the definitive address for that computer network card on the network.

 

Every network card manufactured is supposed to have a unique MAC address. The address looks like this: 00-80-48-32-9B-6B - a combination of 6 hexadecimal numbers. With this information you can easily find out who the manufacturer of your card is and the serial/batch number of it.

 

The first 3 numbers actually represent the company who manufactured your card and their name can be looked up on various MAC address databases on the net by entering those numbers. The last 3 numbers represent the product batch/serial number and is left upon the company to decide how they'd use that part.

One such site which tells you the manufacturer of your card based on the first 3 numbers is: http://www.coffer.com/mac_find/

 

If you want to find out the MAC address of your network card, simply open up a Command Prompt in Windows and type

CONSOLE

C:\> ipconfig /all

Windows 2000 IP Configuration

 

Host Name . . . . . . . . . . . . : sourjya

Primary DNS Suffix . . . . . . . :

Node Type . . . . . . . . . . . . : Broadcast

IP Routing Enabled. . . . . . . . : No

WINS Proxy Enabled. . . . . . . . : No

DNS Suffix Search List. . . . . . : microsys-asia.info

 

Ethernet adapter Local Area Connection:

 

Connection-specific DNS Suffix . : microsys-asia.info

Description . . . . . . . . . . . : Realtek RTL8139(A)-based PCI Fast Et

hernet Adapter

Physical Address. . . . . . . . . : 00-80-48-32-9B-6B

 

As you can see the last line here shows me the physical address or MAC address of my card...

 

This address is used in conjunction with your IP to send/receive packets in your internal network. There are lots of protocols involved in how MAC addresses are used in this regard. In other words, these physical addresses are very essential to the computers to be able to locate each other on an internal network. For more information look-up the RFC (Request For Comment) archives on MAC addresses.

 

Hope this clears things up a bit.

Regards,

m^e

[PathofNeo 0]

Thanks man. That helps quite a bit. Is there a way for you to find out my MAC address or for me to find yours? Is this all stored somewhere?

[WesternWarez 0]

As you can see the last line here shows me the physical address or MAC address of my card...

<{POST_SNAPBACK}>

goto windows start menu click run, type command then typw in ipconfig /all

[OneStopReefShop 0]

Thanks man.  That helps quite a bit.  Is there a way for you to find out my MAC address or for me to find yours?  Is this all stored somewhere?

<{POST_SNAPBACK}>

I'm still a newbie, especially when it comes to more of the "Tricks of the Trade" with computers... but from the information I've been able to find out, it would be extreamly difficult for someone to find out another's MAC address. I'm also not so sure what good that information would do them. Perhaps we can get some much more ed-u-ma-cated types here to help us understand more how this all works???

 

Thanks in advance.

[miCRoSCoPiC^eaRthLinG 0]

As mentioned above - finding out your own MAC address is a one-step job through ipconfig/all - but finding out someone else's MAC address - I'm not so sure of.

 

I don't think it can be done in any easy way or if it can be done at all. To the best of my knowledge - such a thing can be done only if the other computer is a part of your LAN.. and even in that case, you'd have to extensively analyze the packets passing to and fro on your network, and study the headers. Sometimes the packet headers contain the destination computers MAC Address - specially if the LAN is using Microsoft's NetBEUI(NetBIOS) protocol. If it is a TCP/IP based network - forget about MAC addresses... why do you need it anyway ?

[loganbest 0]

There is a way of getting someone else's MAC Address, while it is still illegal, I dont recomend doing to someone with Windows because you have to hack someones computer to get it and with Windows security it will copy all of your information on your computer and send it to microsoft for extensive analyzation. If they do get the info they need to get you in Jail they will do it!

[WeaponX 0]

This is just a hunch, but when I'm connected I see my network and the MAC address of my wireless PC card. I'm using a Netgear WG511 PCMCIA card. I didn't see if I can see other MAC addresses (like the computer in my living room connecting to the network/internet).Hmm. Just curious if it might actually show the MAC address for that other card in the living room PC. I don't think that's illegal since Netgear has it built-in to their software.

[miCRoSCoPiC^eaRthLinG 0]

WeaponX: Why don't you give it a shot and let us know... even I'm interested to find out

[loganbest 0]

You should be able to see the MAC in your livingroom comp if your house is part of a home network (which since you have wireless it probably is)

[WeaponX 0]

WeaponX: Why don't you give it a shot and let us know... even I'm interested to find out

I don't know why I never did this. No problem, I will try to do this if someone uses that living room computer. LOL. Sister has exams so it's been unused for about a week now.
Yes logan, it's in the network at home. I will definitely post a followup to this.

[Casanova1405241497 0]

i think , Short for Media Access Control address, a hardware address that uniquely identifies each node of a network. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI Reference Model is divided into two sublayers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. The MAC layer interfaces directly with the network medium. Consequently, each different type of network medium requires a different MAC layer.On networks that do not conform to the IEEE 802 standards but do conform to the OSI Reference Model, the node address is called the Data Link Control (DLC) address. i think it might be get u some information by this

[jvizueta 0]

The MAC address is a unique value associated with a network adapter. MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN.
MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:

MM:MM:MM:SS:SS:SS

MM-MM-MM-SS-SS-SS

The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,
00:A0:C9:14:C8:29
The prefix
00A0C9
indicates the manufacturer is Intel Corporation.
Why MAC Addresses?
Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.

Notice from moonwitch:

copied from http://forums.xisto.com/no_longer_exists/ credits have been adjusted

[GameUltra 0]

Oh, that's what they are, I always thought it had to do with the Mac(intosh) Operating System. I feel extremely stupid... Well, at least the topic starter didn't know either...

[evought 0]

I'm still a newbie, especially when it comes to more of the "Tricks of the Trade" with computers... but from the information I've been able to find out, it would be extreamly difficult for someone to find out another's MAC address.  I'm also not so sure what good that information would do them.  Perhaps we can get some much more ed-u-ma-cated types here to help us understand more how this all works???

 

Thanks in advance.

1064310962[/snapback]

I you are asking, "How does another computer figure out my address to send data to it?", then the answer depends on the networking protocol. I'll explain how two of them work.

 

First, there is Windows NETBUI or what everyone refers to as "Windows Networking". NETBUI computers do not have IP addresses, they just have names. When you try to connect to a system by name, a request gets broadcast to the network saying "Who answers to 'FRED'S COMPUTER'". The computer that recognizes its own name responds by sending back its MAC address and the connection happens. NETBUI is *really* ineffecient for large networks because of all of this broadcast traffic on every request, although some newer technologies, like Master Browsers and Domain Controllers make it a bit better.

 

The there is TCP/IP, the standard Internet protocol. TCP/IP uses ARP, the Address Resolution Protocol to figure out MAC addresses. When a data packet gets to its final hop (the routing tables say that the target machine is not behind another gateway), an ARP request gets broadcast: "WHO_HAS 212.112.181.001?" The system with that MAC address responds with its physical address, the address gets saved in a table called an ARP cache and the connection proceeds. It actually gets a bit more complex than this with routers and bridges and PPP connections, but you get the idea.

 

So, the short answer is, the sending system broadcasts an ARP request and the receiver sends its MAC address back. This only works on the same physical network. On UNIX or Mac systems, the arp program can be used to display the table of MAC addresses your system currently has cached. ("arp -a" does it on my Macintosh) I think various flavors of Windows have arp as well, but I do not know the right syntax off hand.