Access control with MAC

 In the last article of my series on keeping your kids safe on the Web, I wrote about using a home router for access control. (To read this popular article, click here.) Today I’m going to tell you how to specify a particular computer by using its MAC address. This way, you can build an access control just for your child’s computer.

Tip of the day: take control of your network by learning the MAC addresses. The first concept to understand is that for things to work on a network (whether it’s a small network like you probably have at home, or the great big network we call the “Internet”), each network device must have a unique identifier. This has to be true so that Tom does not receive Mary’s mail, and when you send a document to the printer it does not get sent to the scanner… which wouldn’t know what to do with it. And so we must identify and name devices and locations.

There are three basic ways to identify a device or/and location. Locally attached devices (such as your printer) and “shares” (such as a shared folder) are identified by a universal naming convention (UNC) which uses this format \\server\share. So my HP DeskJet, attached to a PC I’ve named “Paul” can be ‘accessed’ at \\Paul\HP DeskJet; and a shared music folder– named “playlist” — would be found at \\Paul\playlist. (If you’d like to try this, type a location [on your network] into a Run dialogue window.

For those devices that need to communicate across any distance (or, to be available from a distance), and by that I mean “not on your network”, the method is the assigning of an IP address. An IP address is a number somewhat akin to a street address, except it is (typically) “leased” for a short while. To see your current IP address, click here.
The fact that this usually is not a fixed, permanent number, works quite well, as counter-intuitive as that might seem. As long as the number is unique, and stays with you for the duration the communicating devices needs it, your machine will find what it’s looking for. (The reason IP’s cannot be assigned permanently is there is a finite number of them, and there’s more devices than there are numbers.) Typically, your ISP generates a unique IP address for your modem, and they issue another when you need it. This all happens invisibly to you. An IP address looks like 192.168.1.101.

The third element is a permanent identifier, called a MAC address. This can also be called the “hardware address”, which is really what it is — this unique identifier is built into each network interface (the Ethernet port) at the factory. It is a really big number, so there’s plenty of them to go around (well into the future, too). A MAC address looks like 8C:05:F1:23:0E:04.

In the prior article I used a Linksys WRT 54G as my example unit, but this advice will be applicable for pretty much any home router. What you’re going to do is find the MAC on your child’s computer, and then open your router’s control panel and apply restrictions — such as times, “bad” websites, and keywords — just to that address.

1) Go to your child’s PC and open a Command Prompt . Start >Programs >Accessories >Command Prompt (or, Start >Run >”cmd”). Type in “ipconfig /all” (without quotes) and hit Enter, as shown below.

A list of network information will be shown. The number you want is labeled “Physical Address” (the numbers will be separated by hyphens here).
2) log onto your router’s control panel; usually this is accomplished with a browser and requires a password. Specific instructions came with your router, and can also be found on the manufacturer’s website. The picture below shows the access restriction control panel for the Linksys.

Here you would click the “Edit list of PCs” button, and enter (or, select from a list; your router may have already determined the MACs of attached machines) the MAC of your child’s PC.

Now any restrictions you apply will affect only that machine, and your other machines will be unfettered. For a more detailed description of the kinds of restrictions, and how to place them, please refer to the prior article whose link I posted at the top of this post.

I want to thank you all for your patience with the current odd posting times of Tech–for Everyone, and hope that you’ll excuse me if I miss a day. I am –technically speaking– on vacation, after all, and my niece and nephew take priority. I will continue to endeavor to keep to the schedule you have become accustomed to, but…you know.

Copyright 2007 © Tech Paul. All rights reserved.

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