Varma's - "MAC for Little Masters...."

MAC for Little Masters....

Most of you might have heard about, “Mac address” But, how many of you really know what Mac address really is?  

Well, someone has rightly said,

“There is no point in studying a particular thing until you know its implementation in practical life…..”

This post will not only clear your concepts about MAC address but will also teach you what all you can do with this so called “Mac address”.

   -  Parth Varma (Tech Nuske Team)

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What is Mac address?

Mac addresses are also known as the Hardware address, physical address or burned in addresses.

Def:

Mac address is a unique identifier (48 or 64 bit) assigned to network interface (which is hardware) for communication over the physical network segment. 

I hope one of your question (if it rose in your mind) got solved here, that, “Why MAC address is called Physical address or Hardware address”? Right?

But, you might be wondering why it is called, “Burned in addresses”?

Well here is the answer,

Mac addresses are most often assigned by the manufacturer of a network interface card (NIC) and are stored in its hardware; the cards read only memory, or some other firmware mechanism and this is the reason why it is called Burned in addresses. 

If the MAC addresses are assigned by the manufacturer, it will usually contain manufacturers registered identification number.

Remember:

A network node may have multiple NIC’s and will then have one unique MAC address per NIC.

After hearing the definition of MAC, you might be curious to know, “Where is this MAC address used?”

Well, your suspense ends here,

MAC address is used in Media Access Control Protocol sub layer of OSI reference model.

Also, MAC addresses are used in numerous networking technologies including, Ethernet.

Please Note:

MAC addresses are often considered as permanent addresses but even they can be changed under certain circumstances.

Will see this in detail in later post.

In layman’s language, we can assume Ethernet as wire.

                                                                                                                            

                

As we are talking about Ethernet, let me share few words on it:

Systems communicating over Ethernet divide the stream of data into individual packet called frames.

Frames contain the source and destination address and error checking data, so that damaged data can be detected and retransmitted.

Ethernet used coaxial cable initially, then replaced by twisted pair and fiber optics links in conjunction with hubs and switches. 

I hope, now you are clear with Ethernet.

Along with Ethernet we have been using one more word, “NIC”, right from the definition of MAC? How many of you are clear with it?

Well, if you are clear with it, you can skip this topic but for those who want to brushen up this thing, can go through this.

NIC also known as network Interface Card or Network Adapter or LAN adapter is a computer hardware component that connects a computer to computer network.

A bit confused……right?

Don’t worry; let me make it crystal clear.

           

As I said in the definition, NIC is computer hardware (pretty much clear from diagram), that connects a computer to computer network. Here, one end of NIC is connected to our PC while other is connected to the Ethernet (wire) that we have discussed earlier, which further connects to the network i.e. Ethernet is an intermediate thing that connects our PC to Network.

 

Every NIC has a unique 48 bit (6 byte) serial number called MAC address which is stored in ROM.

Every computer on an Ethernet Network must have at least one controller.

NIC allows user to connect to each other either by using cable or wirelessly.

Let's get BACK to MAC.....

How can you get your Mac address?

In windows,

  -     Go to start

  -     Run

  -     Type, cmd

  -     Type. ipconfig/all (no space between)

The one corresponding to physical address is your MAC address.

In linux,

  -     Open terminal

  -     Type, ifconfig

The one corresponding to HWaddr is your MAC address.

Now, let’s move on to some interesting part,

But, but but, before I tell you, “How to change your MAC address you must know, why should we change our MAC address?”

False beliefs about MAC addresses?

Some people think that websites on internet can track users using MAC address and so they must change it!

Well, if you are also in that some people, then let me tell you that you are misguided….

Your MAC address won’t go further than the first router because MAC address is used as unique identifier at data link layer (OSI layer 2), like for example your local Ethernet, while the IP packet being forwarded over internet is at network layer (OSI layer 3) and uses IP address as a global unique identifier (which websites can see and track). And when Ethernet frame reaches a router, the router’s MAC address is used to send the frame forward.

So, clearly this is not a reason to change MAC address.  

So, let’s find it out the real reasons why should you change your MAC address:

  -   Your ISP uses MAC address to identify or authenticate your Internet connection. So, in case, your network card goes boom, the new card you replace it will have different MAC address and so the Internet won’t work. So changing the MAC address to old network adapter is the quickest fix instead of telling your ISP to register your new MAC address which may take a lot of time.

  -   Some internet service providers bind their service to a specific MAC address, if user then changes their network card, the service won’t work anymore. However, changing the MAC address of the new interface will solve the problem.

  -   If you want to access a network, which limits access based on MAC address, from another machine then you can change MAC address to the one for which you have access. Note that only one computer would be able to access the same network (no two computers can have same MAC address on same network to access it without any problem)

  -   Similarly, some software licenses are bound to a specific MAC address.

  -   A very important reason is privacy. Your MAC address can be seen by everyone on the local Ethernet network using many simple tools. A hacker on local network thus can track machines on the network.

  -   If your original MAC address is revealed, a hacker can use it to impersonate you! On many networks access is restricted based on MAC address to avoid access to unauthorized devices on the network. So, when you go offline, someone can use your machine’s MAC address and access the network as ‘you’. 

After reading above points you might say, 

“If we can change the MAC addresses, then how can we use it for authentication purposes?”

Well you are very right. It can be unwise to rely on a single method of authentication.

IEEE 802.1x is an emerging standard better suited to authenticating device at a low level.

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In the next post, I will come back with more interesting topics on MAC, like:

-> How can we change our MAC address?

-> Names of people who wrote their name in history with MAC addresses, and what they did?

and much more.......

don't forget to catch this stuff on next Sunday,  i.e. 15th April, 2012

Till then take care and make it a nice day.....see you soon.

Regards,

Parth Anil Varma

(Tech Nuske)