New England Data Services Blog

What is a MAC Address?

If you are a resident of the United States you probably have a social security number. It is a unique number that is a unique identifier. Nobody else in the world has the same social security number as you. It allows organizations, to track certain information about you.

A MAC Address is basically the same thing, but for computer equipment. The MAC Address is the Media Access Control, which is a unique value assigned to computer hardware for identification purposes. Your network adapters (your Ethernet card and wireless) use MAC Addresses to give you access to certain networks. Most of the time college IT departments require the students to register their MAC Address to allow them access to the network. This way, they can help prevent strangers from getting on the college network. In addition, the college can monitor what is going and coming from the MAC Address to prevent illegal activity.

Using our social security number example, we can pretend that a social security card is like a network card in a computer. Every place we give our SS number to has our information. Likewise, wherever we register the MAC Address of our network card has all the information of our network card.

Despite its purpose of being a unique identifier, most hardware with a MAC address can be changed (MAC spoofing). For example, the MAC Address on an Xbox 360 can be changed relatively easily. This number contains 12 hexadecimal numbers separated in pairs by hyphens. Looking to see what the MAC Address for your network card is? Easy, just open the Command Prompt and type in ipconfig/all. Look to find the Physical Address (MAC Address) corresponding to your Ethernet adapter.

What Is Safe Mode?

So you sit down in front of your computer, turn it on, and you start to hear the Jaws music?!?!?! It gets louder and louder until, the Blue Screen of Death (BSoD) appears on your monitor. It says that your Windows system has been shut down to prevent any further damage. Most of the time, the BSoD appears without any sign of the problem before. Usually it has to do with a recent software or hardware driver installation. It seems pretty ridiculous that you have no way of recovering your system because of the driver for your new USB keyboard had bugs in it. What can you do?

Luckily Windows put in an advanced startup option called Safe Mode. Essentially, this starts up the operating system, but with very simple drivers. Windows boots to a file called system.cb instead of the normal system file. This loads virtual device drivers that can communicate with parts of the computer.

Once in Safe Mode, you can locate and fix the problems with tools like the Device Manager. Safe Mode usually recognizes your wireless and wired Ethernet cards so you can connect to the internet and download the newest device drivers for your hardware if this was the source of the problem. If the problem comes from a recently installed program you can use the Add/Remove Programs.

In addition to a graphical to the Safe Mode, you can also boot Safe Mode with the Command Prompt. If you know there is a corrupted file due to a virus or malware, you can navigate through the directory structure, delete the corrupted files, and replace them with copies of the clean version. This method usually works best with problems due to corruption in the system files or registry.

Custom Built Ethernet Cables

Your company’s office keeps on moving desks and computer around and you find that every time you move, you need a different sized Ethernet cable to reach your desk without leaving a mess of excess cable on the floor. Maybe your office needs to run multiple network cables from one side of the office to the other. At the end of the month, you realize you have spent hundreds of dollars on cable that just needs to be moved next week.

 

Being able to make and fix network cables is a very resourceful technique when it comes to rewiring an office network. All you need is a big spool of quality Ethernet, also known as cat5 cable, RJ-45 connectors (make sure they are compatible with the type of cable you buy), and a crimping/wire cutting tool.

 

The following are a list of steps to making an Ethernet cable:

 

1.   Cut off a piece of cable off the spool to the desired length.

 

2.      Strip no more than an inch of the insulation to expose data wires inside. Depending on the type of crimping tool you get, it may also have a built in cat5 wire stripper that will strip off the perfect amount of insulation. After pulling off the insulation, you will see 8 wires hopefully color coated.

 

3.      You will now have to separate the eight wires into the following order:

NOTE: When you separate the wires, put them side by side.

 

 

White-Orange|Orange|White-Green|Blue|White-Blue|Green|White-Brown|Brown

 

 

 

4.      With the wires lined up, clip the wires so their ends are all even and stick out no more than a ½ inch from the insulation.

 

5.      Hold the RJ-45 connector with the release clip faced toward the ground. You will probably need to pinch the coating so the wires do not move around on you.

 

6.      Carefully insert the wires into the connector, making sure the wires do not change places with each other. Make sure the ends of the wires are touching the ends of the connector.

 

7.      Once the wires are in, push the cable insulation into the connector as far as it will go. If your wires are sticking out of the side of the connector you put them in, they are prone to damage.

 

8.      Before crimping, make sure all the wires are aligned correctly. Insert the RJ-45 connector into the crimping tool and give it a nice firm squeeze. If you over squeeze the crimping tool, the connector will break. Just do the other end of the cable and you are ready to use it.

 

9.      Check cable with a cable tester that is rated for the speed and media of the type of cable being made. A proper cable tester is an instrument called a time-domain reflectometer. They are not inexpensive but a quality unit will last quite some time. A cheap continuity tester is inappropriate and should not be used.

 

With the ability to customize your cables, you can save the time and money of having to go buy new cables every time you change something. Instead of buying 12 7’ cables, buy a 100’ Ethernet cable, split it into 7’ sections, and save roughly $40. You will eliminate the current mess of cable you have tucked behind your desk with the perfect cable length. Finally, you will be able to trouble shoot and fix any problem with any current cable problems you have.

 

Even though it takes time to make your own cables, the money you save and the satisfaction of using your own custom built cables outweighs the time spent.