The end of the beginning.

How to Install BackTrack 5(contents)

►Download the BackTrack 5 ISO
►Setting up a Virtual Machine
►Installing BackTrack 5
►BackTrack Login
►(Optional) Creating a Bootable USB Drive

►Download the BackTrack 5 ISO
Head over to: http://www.BackTrack-linux.org/downloads/ Then click the download button.

After that, you need to pick the version of BackTrack that you want. Pick the latest one, it’s BackTrack 5 R3 at the time of writing this tutorial. The window managers(KDE and Gnome) are both pretty much equal, choose any. Pick the architecture according to your system’s specs(Right click on My computer to find out, 32 bit or 64 bit) . We want the ISO file type because we can use it on a DVD, a USB flash drive, and install on a virtual machine. Direct download or torrent download is up to you. The file is little over 3 GBs, so it may take some time depending on your internet speeds.
(You’re now setting up a whole new operating system, which takes time, So I suggest you read this tutorial before beginning once completely, and then refer to it if you get stuck, it’s relatively easy)

►Setting up a Virtual Machine
A virtual machine (VM) is the software implementation of a physical computer. In other words, it’s having another computer on your current computer. If you have never used a virtual machine it is a good time to start. VMs are excellent when it comes to practicing your hacking techniques as they provide somewhat of a safe closed environment, such that any damage, if it occurs is contained within the dummy operating system, which can then be simply restarted to start afresh.

To start, you’re going to need to get VM software. There are many out there, here are a few popular ones.
VMware Player (Windows/Linux) – Free
VirtualBox (Windows/Mac/Linux) – Free

Whichever VM software you go with, make sure it has a way to network with other VMs. If you don’t want to spend the money, go with VirtualBox. If you plan to get serious with penetration testing, you might want to consider getting a VMware Workstation license. It is full of useful tools and goodies such as sharing VMs and remote access and easy to work with. The easiest to install is ‘Windows Virtual PC’, it will do for beginner purposes. These programs are very similar in function. You shouldn’t have trouble following the basic setup instructions.(Google any Virtual machine software and install it)

After everything is installed and running, click “Create new virtual machine”. (Depending on which one you install, the instructions might be a little different. If you look around there will definitely be similar options).

Next you’re going to select “Installer disc image file” then browse for the BackTrack 5 ISO.
Select the operating system as linux, and the version as Ubuntu.

Give the virtual machine a name such as “BackTrack 5 R3” and select a location for where you want to save the virtual machine files.

When asked how much you want the virtual disk drive to be, you want at least 25 GB. This will be the most demanding requirement of BackTrack 5. Although the BackTrack-linux wiki says you need at least 20 GB, I found you will run out of space by the time you install updates or any other software (Feel free to put in even 5-15 Gb, if you simply want to look around. The OS is not the big, the tools are). Then, you will have the option of storing the virtual disk as a single file, or split into multiple files. Creating a virtual disk as a single file will allocate all of the space right away. Splitting into multiple files means the drive files will grow as you need them. So if your hard drive space is limited on your host system, go with multiple files. If you have a massive drive, and not worried about space, go with a single file.

And that’s it! The virtual machine is ready to go. The recommended minimum RAM is 512 MB, however you can try lower if you need to.
Power on the virtual machine and you will be ready to install BackTrack.

►Installing BackTrack 5
If you are installing on a hard drive, you will need to burn the BackTrack 5 ISO on to a DVD or a USB Drive.
First turn on your machine, then insert your DVD or USB Drive. Then press the key that allows you to select your boot drive. You may have to go into the bios to enable this. Most often, F12 will work. Select either your DVD drive, or your USB Drive to boot from it. (You may simply use the ISO file also. Windows virtua PC, for example gives an option to simply select an ISO file and start up directly)
After a few moments, you will see BackTrack Live CD menu. Press enter on ‘BackTrack Text – Default Boot Text Mode’.

Wait about 10 seconds, and you will come to BackTrack shell console. Type the command “startx” to load the GUI.(If you directly used the ISO file without burning it to anything, your operating system will be now ready. If you prefer to burn the file to a DVD or pen drive follow the steps below)
After another few moments, you will come to the desktop of BackTrack. Double click on the “Install BackTrack” to begin the install process.

After you select your time zone, and language, you then have to partition your drive. If you are using a virtual machine, go ahead and use the whole drive. If you are dual booting, you will have to specify your partition for your two operating systems.

Continue through the installer, and then click finish. BackTrack will then install on to your system. This process takes about 10-15 minutes.

►BackTrack Login
After it is finish, restart your system.
After restarting, you will come to a login screen.

The default root name for BackTrack is “root” and the password is “toor”. After typing in the root username and password, you will come back to the BackTrack shell. Type “startx” to enter the GUI desktop, and we’re done ! I recommend you look around get a feel of all the tools and applications that come pre-installed on the amazing BackTrack OS.

►(Optional)Creating a Bootable USB Drive
Required Items:
A USB flash drive with minimum space of 4 GB.
BackTrack 5 ISO
UNetbooin – ( http://unetbootin.sourceforge.net/ )

UNetbootin is a program that allows you to create bootable USB drives for linux distros and Windows. UNetbootin will download the distribution or use an ISO file you selected from your hard drive.

Once UNetbootin is downloaded you can run it by double clicking (Windows), plug in your USB Drive.
Start UNetbooin and select the “diskimage” option, then select your BackTrack 5 ISO.
Select your USB Drive, then click “OK”.
(WARNING: This will format your USB Drive and remove all previous data.)
Now you should be able to boot off of your USB Drive with BackTrack 5.

How To Manually Remove a Virus From Your Computer

Learn how to manually remove virus easily from your PC by watching this video:

This guide focuses on manually removing viruses and malware from your computer. If you want to use an anti-virus program instead, please check out this tutorial written byBurritobob. This tutorial's best intention is focused around removing RAT and Keylogger viruses.

Step 1
Run msconfig and look for suspicious files. Here we see one. It’s unknown, and it also has a startup key that we’ve never seen until recently. Uncheck it from start up and/or from services.

If you think you are being monitored. Open Command Prompt and do the following

Step 2
Boot into safe mode. This can be done by checking the box in the “boot” tab in msconfig.

Step 3
Run msconfig in safe mode and we can see it’s checked because the virus is persistent. The virus will not be running however, due to the fact that we are currently in safe mode.

Step 4
Navigate to the registry. We are doing this in safe mode because some viruses disable the registry. 
Note: Be sure your folder options are set to show hidden files and folders

Step 5
Navigate to the location of the virus. If you are not sure which one is a virus, locate to all of the following possible locations:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnceEx
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServicesOnce
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Runonce
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServices
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run

Step 6
Section a) if you are unsure if it is a virus of not, right click the suspected file{s} and click modify

Since you are unsure of the integrity of the file, put a “:” in front of the value data. This will disable the start up of the virus but it will still be in your computer.

Section b) if you are certain that you’ve found the virus (like I have in the picture) you can delete the registry entry.

Step 7
Be certain it is gone; it shouldn’t even be listed as a startup item anymore.

Step 8
To be certain, use CCleaner to scan the registry and fix any issues there are.

Recap
Hopefully this should’ve gotten your computer rid of any viruses. It is recommended to download the latest version of an Anti-Virus program and scan your computer fully even after doing this.

Please Note: If you still feel insecure it is recommended to do a clean reinstall of Windows. After reinstalling, install Microsoft Security Essentials as it is the most trusted anti-virus.

Thank you for reading  

 

Can't find your answer ? Ask Americascomputergenius@gmail.com

How To Hack Password Potected Sites

ASKMEWUZUP.BLOGSPOT.COM

1There are many ways to defeat java-script protected web

sites. Some are very simplistic, such as hitting ctl-alt-del

when the password box is displayed, to simply turning off

java capability, which will dump you into t he default page.

You can try manually searching for other directories, by

typing the directory name into the url address box of your

browser, ie: you w ant access to www.target.com . Try typing

www.target.com/images .(almost ever y web site has an images

directory) This will put you into the images directo ry,

and give you a text list of all the images located there.

Often, the t itle of an image will give you a clue to the

name of another directory. ie: in www.target.com/images,

there is a .gif named gamestitle.gif . There is a g ood

chance then, that there is a 'games' directory on the site,

so you wou ld then type in www.target.com/games, and if it is

a valid directory, you aga in get a text listing of all thefiles available there.

For a more automated a pproach, use a program like WEB SNAKE

from anawave, or Web Wacker. These programs will create a

mirror image of an entire web site, showing all director ies,

or even mirror a complete server. They are indispensable for

locating hidden files and directories.

What do you do if you can't get past an openin g "Password

Required" box? First do an WHOIS Lookup for the site. In our

example, www.target.com . We find it's hosted by www.host.com

at 100.100.100. 1. We then go to 100.100.100.1, and then launch \

Web Snake, and mirror the e ntire server. Set Web Snake to NOT

download anything over about 20K. (not ma ny HTML pages are

bigger than this) This speeds things up some, and keeps yo u

from getting a lot of files and images you don't care about.

This can take a long time, so consider running it right before bed time.

Once you have an image of the entire server, you look through

the directories listed, and find /target. When we open that

directory, we find its contents, and all of i ts sub-directories listed.

Let's say we find /target/games/zip/zipindex.html . This would be the index

page that would be displayed had you gone through the

password procedure, and allowed it to redirect you here.

By simply typ ing in the url

www.target.com/games/zip/zipindex.html you will be on

the index page and ready to follow the links for downloading.

ASKMEWUZUP.BLOGSPOT.COM

Backtracking EMAIL Messages

Tracking email back to its source: askmewuzup

cause i hate spammers... Evil or Very Mad

Ask most people how they determine who sent them an email message and the response is almost universally, "By the From line." Unfortunately this symptomatic of the current confusion among internet users as to where particular messages come from and who is spreading spam and viruses. The "From" header is little more than a courtesy to the person receiving the message. People spreading spam and viruses are rarely courteous. In short, if there is any question about where a particular email message came from the safe bet is to assume the "From" header is forged.

So how do you determine where a message actually came from? You have to understand how email messages are put together in order to backtrack an email message. SMTP is a text based protocol for transferring messages across the internet. A series of headers are placed in front of the data portion of the message. By examining the headers you can usually backtrack a message to the source network, sometimes the source host. A more detailed essay on reading email headers can be found .

If you are using Outlook or Outlook Express you can view the headers by right clicking on the message and selecting properties or options.

Below are listed the headers of an actual spam message I received. I've changed my email address and the name of my server for obvious reasons. I've also double spaced the headers to make them more readable.

Return-Path:

X-Original-To: davar@example.com

Delivered-To: davar@example.com

Received: from 12-218-172-108.client.mchsi.com (12-218-172-108.client.mchsi.com [12.218.172.108])

by mailhost.example.com (Postfix) with SMTP id 1F9B8511C7

for ; Sun, 16 Nov 2003 09:50:37 -0800 (PST)

Received: from (HELO 0udjou) [193.12.169.0] by 12-218-172-108.client.mchsi.com with ESMTP id <536806-74276>; Sun, 16 Nov 2003 19:42:31 +0200

Message-ID:

From: "Maricela Paulson"

Reply-To: "Maricela Paulson"

To: davar@example.com

Subject: STOP-PAYING For Your PAY-PER-VIEW, Movie Channels, Mature Channels...isha

Date: Sun, 16 Nov 2003 19:42:31 +0200

X-Mailer: Internet Mail Service (5.5.2650.21)

X-Priority: 3

MIME-Version: 1.0

Content-Type: multipart/alternative; boundary="MIMEStream=_0+211404_90873633350646_4032088448"

According to the From header this message is from Maricela Paulson at s359dyxxt@yahoo.com. I could just fire off a message to abuse@yahoo.com, but that would be waste of time. This message didn't come from yahoo's email service.

The header most likely to be useful in determining the actual source of an email message is the Received header. According to the top-most Received header this message was received from the host 12-218-172-108.client.mchsi.com with the ip address of 21.218.172.108 by my server mailhost.example.com. An important item to consider is at what point in the chain does the email system become untrusted? I consider anything beyond my own email server to be an unreliable source of information. Because this header was generated by my email server it is reasonable for me to accept it at face value.

The next Received header (which is chronologically the first) shows the remote email server accepting the message from the host 0udjou with the ip 193.12.169.0. Those of you who know anything about IP will realize that that is not a valid host IP address. In addition, any hostname that ends in client.mchsi.com is unlikely to be an authorized email server. This has every sign of being a cracked client system.

Here's is where we start digging. By default Windows is somewhat lacking in network diagnostic tools; however, you can use the tools at to do your own checking.

davar@nqh9k:[/home/davar] $whois 12.218.172.108

AT&T WorldNet Services ATT (NET-12-0-0-0-1)

12.0.0.0 - 12.255.255.255

Mediacom Communications Corp MEDIACOMCC-12-218-168-0-FLANDREAU-MN (NET-12-218-168-0-1)

12.218.168.0 - 12.218.175.255

# ARIN WHOIS database, last updated 2003-12-31 19:15

# Enter ? for additional hints on searching ARIN's WHOIS database.

I can also verify the hostname of the remote server by using nslookup, although in this particular instance, my email server has already provided both the IP address and the hostname.

davar@nqh9k:[/home/davar] $nslookup 12.218.172.108

Server: localhost

Address: 127.0.0.1

Name: 12-218-172-108.client.mchsi.com

Address: 12.218.172.108

Ok, whois shows that Mediacom Communications owns that netblock and nslookup confirms the address to hostname mapping of the remote server,12-218-172-108.client.mchsi.com. If I preface a www in front of the domain name portion and plug that into my web browser, http://www.mchsi.com, I get Mediacom's web site.

There are few things more embarrassing to me than firing off an angry message to someone who is supposedly responsible for a problem, and being wrong. By double checking who owns the remote host's IP address using two different tools (whois and nslookup) I minimize the chance of making myself look like an idiot.

A quick glance at the web site and it appears they are an ISP. Now if I copy the entire message including the headers into a new email message and send it to abuse@mchsi.com with a short message explaining the situation, they may do something about it.

But what about Maricela Paulson? There really is no way to determine who sent a message, the best you can hope for is to find out what host sent it. Even in the case of a PGP signed messages there is no guarantee that one particular person actually pressed the send button. Obviously determining who the actual sender of an email message is much more involved than reading the From header. Hopefully this example may be of some use to other forum regulars.

The performance of computer systems has been steadily increasing as faster processors, memory, and video cards are continuously being developed. The one key component that is often neglected when looking at improving the performance of a computer system is the hard drive. Hard drive manufacturers have been constantly evolving the basic hard drive used in modern computer systems for the last 25 years, and the last few years have seen some exciting developments from faster spindle speeds, larger caches, better reliability, and increased data transmission speeds.

The drive type used most in consumer grade computers is the hardy ATA type drive (commonly called an IDE drive). The ATA standard dates back to 1986 and is based on a 16-bit parallel interface which has undergone many evolutions since its introduction to increase the speed and size of the drives that it can support. The latest standard is ATA-7 (first introduced in 2001 by the T13 Technical Committee (the group responsible for the ATA standard)) which supports data transfer rates up to 133MB/sec. This is expected to be the last update for the parallel ATA standard.
As long ago as 2000 it was seen that the parallel ATA standard was maxing out its limitations as to what it could handle. With data rates hitting the 133MB/sec mark on a parallel cable, you are inviting all sorts of problems because of signal timing, EMI (electromagnetic interference) and other data integrity issues; thus industry leaders got together and came up with a new standard known as Serial ATA (SATA). SATA has only been around a few years, but is destined to become “the standard” due to several benefits to be addressed in this Tech Tip.

The two technologies that we will be looking at are:

ATA (Advanced Technology Attachment)– a 16-bit parallel interface used for controlling computer drives. Introduced in 1986, it has undergone many evolutions in the last 18+ years, with the latest version being called ATA-7. Wherever an item is referred to as being an ATA device, it is commonly a Parallel ATA device. ATA devices are also commonly called IDE, EIDE, Ultra-ATA, Ultra-DMA, ATAPI, PATA, etc. (each of these acronyms actually do refer to very specific items, but are commonly interchanged)
SATA (Serial Advanced Technology Attachment)– a 1-bit serial evolution of the Parallel ATA physical storage interface.

Basic Features & Connections

SATA drives are easy to distinguish from their ATA cousins by the different data and power connections found on the back of the drives. A side-by-side comparison of the two interfaces can be seen in this PDF from Maxtor, and the following covers many of the differences…
Standard ATA drives, such as this 200GB Western Digital model, have somewhat bulky, two inch wide ribbon cable with 40-pin data connections and receive the 5V necessary to power them from the familiar 4-pin connection. The basic data cables for these drives have looked the same for years. A change was made with the introduction of the ATA-5 standard to better improve the signal quality by making an 80 wire cable used on the 40-pin connector (these are commonly called 40-pin/80-wire cables). To improve airflow within the computer system some manufacturers resorted to literally folding over the ribbon cable and taping it into that position. Another recent physical change also came with the advent of rounded cables. The performance of the rounded cables is equal to that of the flat ribbon, but many prefer the improved system air flow afforded, ease of wire management, and cooler appearance that come with them.
SATA drives, such as this 120GB Western Digital model, have a half inch wide, 7 “blade and beam” data connection, which results in a much thinner and easier to manage data cable. These cables take the convenience of the ATA rounded cables to the next level by being even narrower, more flexible and capable of being longer without fear of data loss. SATA cables have a maximum length of 1 meter (39.37 inches), which is much greater than the recommended 18 inch cable for ATA drives. The reduced footprint of SATA data connections frees up space on motherboards, potentially allowing for more convenient layouts and room for more onboard features!
A 15-pin power connection delivers the 250mV of necessary power to SATA drives. 15-pins for a SATA device sounds like it would require a much larger power cable than a 4-pin ATA device, but in reality the two power connectors are just about the same height. For the time being, many SATA drives are also coming with a legacy 4-pin power connector for convenience.
Many modern motherboards, such as this Chaintech motherboard, come with SATA drive connections onboard (many also including the ATA connectors as well for legacy drive compatibility), and new power supplies, such as this Ultra X-Connect, generally feature a few of the necessary 15-pin power connections, making it easy to use these drives on new systems. Older systems can easily be upgraded to support SATA drives by use of adapters, such as this PCI slot SATA controller and this 4-pin to 15-pin SATA power adapter.
Optical drives are also becoming more readily available with SATA connections. Drives such as the Plextor PX-712SA take advantage of the new interface, although the performance will not be any greater than a comparable optical drive with an ATA connection.

Performance

In addition to being more convenient to install and drawing less power, SATA drives have performance benefits that really set them apart from ATA drives.

The most interesting performance feature of SATA is the maximum bandwidth possible. As we have noted, the evolution of ATA drives has seen the data transfer rate reach its maximum at 133 MB/second, where the current SATA standard provides data transfers of up to 150 MB/second. The overall performance increase of SATA over ATA can currently be expected to be up to 5% (according to Seagate), but improvements in SATA technology will surely improve on that.

The future of SATA holds great things for those wanting even more speed, as drives with 300 MB/second transfer rates (SATA II) will be readily available in 2005, and by 2008 speeds of up to 600 MB/second can be expected. Those speeds are incredible, and are hard to imagine at this point.

Another performance benefit found on SATA drives is their built-in hot-swap capabilities. SATA drives can be brought on and offline without shutting down the computer system, providing a serious benefit to those who can’t afford downtime, or who want to move drives in and out of operation quickly. The higher number of wires in the power connection is partially explained by this, as six of the fifteen wires are dedicated to allowing the hot-swap feature.

Price

Comparing ATA drives to SATA drives can be tricky given all of the variables, but in general it is the case that SATA drives will still cost just a bit more than a comparable ATA drive. The gap is closing rapidly though, and as SATA drives gain in popularity and availability a distinct shift in prices can be expected. Considering the benefits of SATA over ATA, the potential difference of a few dollars can easily be justified when considering an upgrade.

Final Words

The current SATA standard provides significant benefits over ATA in terms of convenience, power consumption and, most importantly, performance. The main thing ATA has going for it right now is history, as it has been the standard for so long that it will not likely disappear any time soon. The future of SATA will be even more interesting as speed increases will help hard drive development keep pace with other key system components.

The power coming into a computer is the most critical component, and it may be one of the most overlooked. It is just taken for granted that it will always be there and working properly. A top of the line processor and ultra powerful video card do nothing if a system does not receive the ample, stable power it demands. Having quality components providing and regulating the power supplied to a computer is critical, and this brief overview looks at a few areas worth consideration.

Power Supplies

Computer power supplies take the high (110V or 220V) AC voltages from an electrical outlet and convert it to the various lower DC voltages required for a system to operate. The typical voltages required inside a computer are 3.3V, 5V, and 12V, where the 3.3V and 5V lines are generally used to power circuitry, and the 12V line provides power to run items such as hard drives, optical drives, and cooling fans.
Power supplies are sold in terms of their total power output, in terms of wattage. Choosing the correct power supply means not only finding one that will provide enough power for all of the components connected to the system, but also one that is the correct size physically, has enough connections for typical drives and fans, and if necessary, that also has special connections for things such as Serial ATA drives and modern video cards.
Choosing a power supply with enough power shouldn’t be much of a problem, as having more power than you need is never a bad thing. Just because a power supply is rated for 400W, or perhaps 600W, does not imply that it is drawing that at any given time. It just indicates the total power available to the various lines inside the computer. For those interested in getting a good idea of their minimum power requirements, this Power Wattage Calculator is a convenient reference. In addition to checking out the total wattage of a power supply, looking for strong amperage ratings on the 3.3V, 5V, and 12V lines is also recommended, as power supplies with identical total power ratings may distribute the power to the various lines in different quantities.
Power supplies come in a few different physical sizes, but the most common are designed to fit the standard ATX and micro ATX (mATX) form factor cases. A typical ATX power supply, such as this Echo-Star 680W unit, measures 3.25” x 6” x 5.5” and features two cooling fans to not only cool the power supply, but to also help draw hot air out of the computer. A typical mATX power supply, such as this A-Power 320W unit, measures 2.5” x 5” x 4” and due to the smaller size features just one cooling fan. mATX cases are generally much smaller than ATX cases, and therefore have smaller power supplies, with generally lower power ratings, and fewer connectors.
The connectors on a power supply also deserve consideration. Most power supplies come with what looks to be an electric octopus of wires hanging off the back surface, and you need to make sure that somewhere in that tangled bundle are all of the connectors you need. The power supply should at least have as many connections as the number of drives, cooling fans, and other items found in the case. Up until recently power supplies had a fixed number of connections, and if you needed more, you needed to use splitters to distribute the power to all the components. Modular power supplies, such as the Ultra X-Connect 500W unit, are now available that eliminate that “electric octopus” all together, and allow the end user to connect just the cables they need. The flexibility of a modular power supply design not only lets you customize the connections to your needs, it also makes for a simple and tidy installation, since there are no extra wires dangling inside the case.
The selection of a high quality power supply may cost more money up front, but down the road it could wind up saving money. Many manufacturers now offer power supplies that consume less energy thanks to high quality internal components, advanced designs, and active power factor correction. These units are now able to provide the same power to the components in a computer, but due to increased efficiency, draw less power from the electrical outlet.

Surge Protectors

Surge protectors are intended to protect your electronics from a brief increase in voltage caused by such things as lightning, rolling blackouts, and heavy drawing electrical equipment. A surge protector reacts to divert the extra electricity to ground, and thus protects your expensive computer equipment from damage. A surge is any increase lasting three nanoseconds or longer, so a surge protector needs to react quickly. Most surge protectors also include a fuse (or breaker), and if the surge is too great to be handled without interruption, the fuse will blow. Although the fuse may be destroyed, it’s a small loss compared to what it may have saved.

Surge protectors come in all shapes and styles. Some basic models can even be found at your local dollar store, but offer no more than a few outlets connected to a breaker. No serious protection is obtained, but many people just want more outlets, not protection.
More serious surge protectors will probably cost a bit more than a dollar, but will offer some peace of mind that your equipment is actually being protected. In addition to protecting from electrical surges, some devices include extra features such as conditioning to filter out line noise and ports to protect other lines such as cable television, telephone, and networking.
The Fellowes Smart Surge Power Strip protects up to 10 devices from surges, as well as offering line conditioning and ports to protect your phone line. A highly appealing feature of such a surge protector is that 4 of the ports are designed to accept bulky AC adaptors. For those with surge protectors that weren’t designed to be this user friendly, there is still hope in the form of Power Strip Saver Cables. Basically just 7 inch long extension cords, these items can come in very handy when trying to connect multiple AC adaptors to a more traditional surge protector.

Uninterruptible Power Supplies

Many people familiar with Uninterruptible power supplies (UPS) know that they can keep a computer up and running during a total power failure, but don’t know what else they do. Most UPSes will also provide protection from voltage surges and sags (when the voltage drops below normal), as well as protection from the possibility of a shift in the electricity’s frequency.

UPSes come in two varieties, standby and continuous, although standby versions are far more common and less expensive. A standby UPS allows the devices connected to it to run from the normal electrical connection until a loss of power is detected, at which point it quickly (in a matter of milliseconds) switches to the battery backup of the UPS. A continuous UPS always has the devices connected to it running off of battery power, while the batteries are recharged by the normal electrical connection.
UPSes are sold in terms of their capacity, in terms of VA (voltage multiplied by amperage). This implies that devices connected to the UPS can draw a maximum of so much amperage at a specific voltage. A run time after a power failure is also generally specified for a UPS based on a full load being placed on the device.
Selecting a UPS needs to be based on the intended use… A smaller unit, such as the Fenton 600VA, would be adequate for powering a typical desktop computer, monitor, and smaller peripherals such as a printer and lighting for what they rate as 15-23 minutes at full load. If multiple systems need to be powered, or perhaps there are plans for future expansion that will add to the power demands, a larger unit such as the Tripp Lite 1500VA may be more appropriate. The first two units are intended to be set in close proximity to the devices to be powered, perhaps on the floor behind a desk, but if you are seeking to add a UPS to a server, there are also rackmount solutions such as the Opti-UPS 1100VA.
No matter the application, sizing a UPS may seem overwhelming. One manufacturer, APC, has created a handy UPS Selector Application which will take some of the guess work out of choosing the right UPS for any particular application.

Final Words

A computer system is only as strong as its weakest feature, and many times that distinction falls on the power supply and related components. By choosing a quality power supply, surge protector, and perhaps a UPS, one can make sure that they have adequately strong and stable power to keep their system running now, as well as down the road when upgrades may increase the demand on their system.

Tech Tip
The data on your hard drive is the most critical item inside your computer, and the only item which can not be replaced. It may be an unwanted hassle and expense to replace a defective memory module, monitor, or processor, but there is no replacing data once lost.
In addition to the possibility of a simple hard drive failure, the threat of internet borne worms and viruses has become an increasing risk to data loss or corruption. Although you may not be able to provide absolute protection to your hard drive, there are various ways that you can ensure that the data on your hard drive is protected. Five methods of backing up your data are summarized below.

1. USB Flash Drives

Although I am not recommending that flash drives be used for the actual data storage, they are a convenient means of transferring data from one computer to another. Important files can be quickly loaded onto a device such as the MINIDISK-512-DGRY-CS USB 2.0 Flash Drive, and transported to another computer for safe keeping. Installation and operation is extremely simple, and other than perhaps having to install a software driver, the use of a USB flash drive is a matter of having an available USB port on your computer. Just about every computer produced over the last several years has USB ports included, with more modern systems supporting the USB 2.0 standard. USB 2.0 allows for data transfer rates of up to 480 MB/s, which is a tremendous improvement over the original USB speed limit of 12 MB/s, and allows a user to fill their drives with data in a relatively short period of time.

Although the storage capacity of flash drives has increased greatly over the last year or so, users are still limited to common sizes of 512MB and 1GB. Mass storage is obviously not an option, but even 512MB may be enough to backup your "My Documents" folder, several albums of MP3s, or other important files to be stored elsewhere.

2. CD and DVD Writers/Re-Writers

The falling prices of CD and DVD writers/re-writers have made them a staple of just about every modern computer. These devices can typically be found installed in a computer case, but external devices supporting USB 2.0 or Firewire are available for greater flexibility and ease of installation.
A combination drive, such as theNU Technology DBW-521, will provide the user a high speed CD reader/writer, as well as a DVD reader, for under $40. The extremely low price of the drive (and the blank media) makes for an inexpensive means of creating data backups, and the re-writable media increases the convenience by allowing the same disc to be erased and reused many times. The main limitation of using a CD writer for data backups is that the discs are generally limited to a capacity of 700MB per disc. Not nearly enough for a full backup, but adequate for archiving key files.
The popularity of DVD writers/re-writers has surged thanks to dropping prices, and they are pushing the stand alone CD burner towards extinction. DVD media affords the user far more storage capacity than a CD, and DVD burners can generally burn CDs as wells as DVDs. The recent availability of double layer DVD burners, such as the Sony DW-D22A-DO-N, represents a large boost in the capacity of writable DVDs, taking the previous limit of 4.7GB per disc and nearly doubling it to 8.5GB.
With proper storage, CD/DVD media can provide long term storage that can not be jeopardized by hardware failure. The data on a CD or DVD can easily be read by just about any computer, making it a good choice for archiving files that aren't excessively large.

3. External Hard Drives

As the name might imply, external hard drives are generally the same type of drive you might find inside your system, but housed in a smaller, external enclosure of its own. The enclosure will feature at least one data interface (such as Firewire, USB, or Ethernet), and the capacity is only limited by the size of hard drives presently available and the user's budget.
The Ximeta NetDisk is an example of an external hard drive that provides a user the option of connecting an additional 80GB, 120GB, or 160GB of storage to their system by using either a USB 2.0 or Ethernet connection. Installation for such a device is rather simple, and may involve the installation of some basic software, as well as making the necessary connections between the computer and the external enclosure.
The capacity of external hard drives makes them ideal for backing up large volumes of data, and many of these devices simplify the process by including software (or hardware) features to automate the backup.
For example, some Seagate External drives feature a "one-button" backup option right on the case.In addition to being a convenient method of backing up large volumes of files locally, most external hard drives are compact enough to be portable. The inclusion of a common data transfer interface, such as USB, allows an external hard drive to be connected to just about any modern computer for data transfer, or for more than one computer to share the external hard drive as a back up.

4. Additional Hard Drives

By simply adding an additional hard drive to you system, you can protect yourself from data loss by copying it from your primary drive to your secondary drive. The installation of a second hard drive isn't difficult, but does require a basic understanding of the inner working of a computer, which may scare off some users. We do offer a "how-to" section on our site for many tasks such as installing a hard drive into a computer system.
To take the installation of a second hard drive to another level of security and reliability, the hard drives may be installed in a RAID array. RAID stands for a Redundant Array of Independent (or Inexpensive) Disks, and can be configured in several manners. A thorough discussion of RAID and all of its variations would be an article all by itself, but what may be of interest to this discussion is what is known as RAID 1. A RAID 1 array requires two hard drives of equal size to be installed on a RAID controller, which will then mirror one drive to the other in real time. Many motherboards now come with RAID controllers onboard, but the addition of a PCI slot controller card, such as the Silicon Image Sil0680, is an inexpensive purchase that will add RAID to any system. With a RAID 1 array in place, if one hard drive should ever fail, the system won't miss a best by continuing to run on the remaining good drive, and alert the user that one drive may need to be replaced.

5. Online Storage

Online services, such as Xdrive, allow users to upload their files to a server for safe keeping. Although it may be convenient to have the data available wherever an internet connection is available, there are a few limitations.

The services generally charge a monthly fee relative to the amount of storage space required. At Xdrive, for example, 5GB of storage costs $9.95 per month, which can quickly add up to more than one would spend on any of the other options discussed.

Security is supposed to be very tight on these services, but no matter how secure it may seem, it is still just a password keeping prying eyes from your potentially sensitive documents.

The speed of your internet connection will also weigh heavily on the convenience of your backup, and no matter what type of connection you have; it can't compete with local data transfer rates.

Final Words

Although not a comprehensive list of options available for backing up your data, the five items listed provide some simple and relatively affordable means to ensure that your data is not lost. Data loss is an extremely frustrating and potentially costly situation, but one that can be avoided.

In the previous section we reviewed several aspects of the Transport Layer. We learned a great deal of information; covering sockets, ports, TCP, UDP, segments, and datagrams. Now we will take a look at the fourth and final layer of the TCP/IP stack: the Application Layer.

What Does The Application Layer Do?

A lot of newcomers to TCP/IP wonder why an Application Layer is needed, since the Transport Layer handles a lot of interfacing between the network and applications. While this is true, the Application Layer focuses more on network services, APIs, utilities, and operating system environments.

If you know the TCP/IP stack and OSI model well enough, you’ll know that there are three OSI model layers that correspond to the TCP/IP Application Layer.

By breaking the TCP/IP Application Layer into three separate layers, we can better understand what responsibilities the Application Layer actually has.
The OSI Equivalent of the TCP/IP Application Layer

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• 1. Application Layer - The seventh OSI model layer (which shouldn’t be confused with the TCP/IP stack’s Application Layer). It supports network access, as well as provides services for user applications.
  
  
• 2. Presentation Layer - The Sixth OSI model layer is the Presentation Layer. It translates data into a format that can be read by many platforms. With all the different operating systems, programs, and protocols floating around, this is a good feature to have. It also has support for security encryption and data compression.
  
  
• 3. Session Layer - The fifth layer of the OSI model is the Session Layer. It manages communication between applications on a network, and is usually used particularly for streaming media or using web conferencing.
  

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To better grasp the concepts of the Application Layer, we’ll take a look at a few examples of the Application Layer in action.

Application Layer APIs

If you aren’t hip on the nerdy lingo- don’t worry: an API simply stands for Application Programming Interface. An API is just a collection of functions that allows programs to access an internal environment.

A good example of an API is DirectX. If you’ve ever run a multimedia application and used Windows at the same time, odds are you have come into contact with DirectX. DirectX is made up of many different components that allow programmers to create multimedia applications (such as video games).
There are many types of APIs to delve into. You may have heard of NetBIOS, Winsock, or WinAPI among others. The world of APIs has also extended to web services. You may have heard of a Google API, for instance. In this case Google allows developers to use its internal functions, yet also keeps Google’s internal code safe from prying eyes. (Otherwise, there would be a few security concerns on Google’s part.)

Network Services

The Application Layer handles network services; most notably file and printing, name resolution, and redirector services.

Name resolution is the process of mapping an IP address to a human-readable name. You may be familiar with the name Google more so than the IP address of Google. Without name resolution, we would have to remember four octets of numbers for each website we wanted to visit- not very friendly is it?
A redirector, otherwise known as a requester, is a service that is largely taken for granted. It is a handy little service that looks at requests a user may make: if it can be fulfilled locally, it is done so. If the request requires a redirection to another computer, then the request is forwarded onto another machine. This enables users to access network resources just like they were an integral part of the local system. A user could browse files on another computer just like they were located on the local computer- obviously redirector services are fairly powerful.
Lastly we have file and print services. If a computer needs to access a file server or a printer, these services will allow the computer to do so. It is fairly self-explanatory, but worth reviewing nonetheless.

Network Utilities

This is where most people have experience- within the network utilities section of the Application Layer. Every time you use a Ping, Arp, or Traceroute command, you are taking full advantage of the Application Layer.

It’s quite convenient that the Application Layer is located on the top of the TCP/IP stack. We can send a Ping and, if successful, can verify that the TCP/IP stack is successfully functioning. It’s a good idea to commit each utility to memory, as they are very useful for maintaining, configuring, and troubleshooting networks. Listed below are seven of the most used utilities.
Seven TCP Utilities Explained

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• 1. ARP - Arp stands for Address Resolution Protocol. It is used to map an IP address to a physical address found on your NIC card. Using this command can tell us what physical address belongs to which IP address.
  
  
• 2. Netstat - Netstat is a handy tool that displays local and remote connections to the computer. It displays IP addresses, ports, protocol being used, and the status of the connection.
  
  
• 3. Ping - Ping is a simple diagnostic tool that can check for connectivity between two points on a network. It is one of the most used TCP/IP utilities when setting up a network or changing network settings.
  
  
• 4. TraceRT - Tracert, or traceroute, is a command that will show the path that packets of data take while being sent. It’s handy for checking to see where a possible network failure lies, or even for ensuring that data packets are taking the fastest route possible on a network.
  
  
• 5. FTP / TFTP - FTP and TFTP are both used for transferring files. It is important to note that FTP is a TCP utility, while TFTP is a UDP utility. TFTP tends to be less secure than FTP, and is generally only used for transferring non-confidential files over a network when speed is concerned.
  
  
• 6. Hostname - Hostname is a simple command that displays the hostname of the current computer. Simple, yet effective.
  
  
• 7. Whois - Whois information is just like an online phonebook. It shows the contact information for owners of a particular domain. By using a Whois search, you will find that Google is based in California.
  

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Closing Comments

The Application Layer isn’t as exciting as the others. We don’t really have much physical interaction with the Application layer, and most of the fun applies to developers and geeks only.
There is still much to learn- TCP/IP is just the very beginning of the networking world. But with this lesson on the final TCP/IP layer complete, you can now say that you have a much better understanding of the TCP/IP model. (And networking in general.)

A network interface card, abbreviated as NIC, is what a computer uses to communicate with other computers on a network. Without some type of network interface card installed, your computer will not be able to communicate over a network. Obviously, most of networking revolves around this quaint little device- so it’s good to know what it does and doesn’t do.

How the Network Interface Card Works

The network interface card operates on layer two of the OSI model- the Data Link Layer. They reside on this layer because they work with media access control addresses (abbreviated as MAC). Every single NIC has a unique number on it. This number is burned into the card at the factory in which it is made, and it can’t be changed. This is to ensure that every computer that connects to a network will be unique- and thus, no “Who’s who” problems will exist.

The MAC address of a NIC is displayed as six two-digit hexadecimal numbers, separated by colons. And although we do need a unique MAC address for each computer, it often doesn’t matter since logical addresses (Such as an IP address) are almost always used, as compared to physical addresses, on large networks.

What to Look for in a NIC

There are three primary things to look for in a network interface card: the bandwidth it supports, the type of media is supports, and the type of network architecture it supports.

Bandwidth

Bandwidth is the term we use to describe how much information can flow through a network connection at a given period of time. You can think of it as a pipe in which water is flowing through. We would of course want the larger pipe, so that we may have more water at a faster rate.
When we refer to bandwidth, we generally group it into four different units: bits, kilobits, megabits, and gigabits. If you are using 10BASE-TX Ethernet cable, you are getting 100 Mbps (theoretically). If your NIC card only supports 10 Mbps, you wouldn’t be able to take advantage of the cable’s speed. Obviously, buying such a NIC would be a poor decision.

Type of Media

Some NICs are only able to work on certain types of media. A NIC that only works on Ethernet cable, for instance, will not be able to use wireless or fiber optic media. It will instead be limited to copper connections.
Some NICs can double over as a two cards in one- it isn’t uncommon to see a NIC these days with an optional wireless component. However, it is still important that the type of media your network is using corresponds to the type of media your NIC card agrees with- or else you’ll be searching for that receipt.

Network Architecture

Lastly, we have network architecture. This is both the physical and logical design of the network. Cables, hardware devices, network topology, protocols, and other equipment all fall into this category. The NIC will, in this instance, need to be compatible with everything else on the network.
This category is kind of a given- but Cisco still defines network architecture as one of the three primary things a NIC card buyer needs to know. And hey- if it’s going to be on the exam, we might as well commit it to memory.

When to Replace a NIC

Replacing a network interface card is usually common sense. Cisco likes to go into specifics, however, and demands that students know exactly at what point the replacement should take place. Generally, you should replace the NIC if you think the NIC is damaged. You may also add a secondary NIC for backup. Lastly, you’ll need to replace a NIC if your network changes and your current NIC doesn’t have the specifications to make the transition (example being a transition from copper media to wireless).

A hub and switch essentially accomplish the same thing, although their methods are different. Both can be used to regenerate degraded signals (acting as a repeater), and both can be used to split a signal into multiple signals (handy for splitting up an internet connection to your home network, for instance). But should you really care how they do it? If they both accomplish the same thing, what’s the difference?

What is a Hub?

Think of a hub as a rather naïve device- it operates on the Physical Layer of the OSI model. Switches, on the other hand, are much more intelligent- and operate on the Data Link Layer of the OSI model.

When a hub receives information on one port, the information is then broadcasted to all of its ports. This wouldn’t be such a bad plan if it didn’t waste bandwidth and cause collisions. Imagine if two computers transmitted data at the same time: the packets of information would collide and the information would be corrupted. We would have to rebroadcast the data through the process of Ethernet Carrier Sense Multiple Access with Collision Detection- but you can just call it CSMA/CD. In simple terms, it is the protocol we use to resend data after a collision occurs.
Collisions are obviously a problem with hubs, but we just hit the tip of the iceberg. More importantly, hubs are notorious for wasting bandwidth. Hubs operate at half-duplex, which means data can only flow one way at a time. (As compared to full-duplex, where we can send and receive data between two devices at the same time.) Since we are operating at half-duplex, the bandwidth must be shared between each port on the hub. Imagine you have a 20 port hub with a 20Kb/s line to share. Tough luck, but you’ll only get 1Kb/s to each computer on the network.

What is a Switch?

A switch operates on the Data Link Layer of the OSI model. This means that switches are fairly smarter than hubs, as they can route data on a dynamic level. If information is destined for computer A, for example, the switch will only send the data to computer A.

This addresses our collision problem, since switches use what is called microsegmentation. Microsegmentation will allow for multiple collision domains. Which would you rather have- one collision domain or many?
Let’s look at an example. In the below diagram, there are many collision domains (or segments) for the switch network. If computer A and computer B sent data to each other at the same time, for instance, you may have a collision. Computer A and computer C or D, however, will not experience a collision in the process. In the hub network, there is just one collision domain. That means if the first computer wants to transmit data, it could be interrupted by any of the other computers on the network.

But the fun doesn’t stop there! Switches can keep track of which computer address belongs to a certain port. If there is information destined for computer A, it will only travel through computer A’s port. Remember how the hub split the bandwidth between each port? Microsegmentation allows for us to keep the bandwidth as high as possible for each computer. If you have a 20Kb/s line coming in, each computer can have the full 20Kb/s. (But note that switches aren’t magic, if two or more computers are using the line at the same time, they must share it. Still- this is much better than hubs, which automatically split up bandwidth to ports that you might not even be using!)

Should You Upgrade to a Switch?

The short answer here is: definitely. Hubs were primarily used because they are inexpensive and easy to setup. The good thing about “dumb” devices is that they don’t require much configuration or maintenance.
Switches are a bit more expensive, and allow for more configuration options. They can be programmed much like routers, something hubs can’t accomplish. The average home user likely won’t need the extra configuration options- but they will appreciate the speed. If your network is already blazing fast, you may not need the upgrade. If you could appreciate some extra performance, or if you have many computers on the same network, then the upgrade is almost mandatory.

Imagine you’re Paul Revere, riding from Boston to Lexington to warn citizens that the redcoats were coming. He may not be as fast as computer networks today, but Paul Revere was essentially acting much like a broadcast would- he was relaying his message to the entire town of Lexington.

A broadcast, in particular, is a simple message that is sent to all clients on a local area network. But just exactly what enables a network to broadcast a message to every single client on the network?

What is a Broadcast Address?

A broadcast address is an address used to indicate that information being sent out should be delivered to every client on the local area network. These addresses are always the highest number possible in a particular network address or subnet. We’ll cover subnets later, for now let’s take a closer look at the most common broadcast address: Data Link Layer broadcasts.

Broadcasts on the Data Link Layer correspond to MAC addresses. MAC address broadcasts are generally the easiest to understand, since they aren’t affiliated with IP addresses or subnetting. In fact, all you really need to remember is FF:FF:FF:FF:FF:FF. Whereas this MAC address would normally be comprised of different hexadecimal values, it is instead simply all F’s. (As we know, each F stands for the highest number in hexadecimal: 15)

When a MAC address broadcast is sent out, each network interface card on the local area network will see the broadcast address and automatically pass the information up to the upper layers of the OSI model. So far it’s simple- right? Now let’s get back to the subnetting and IP address topics that are present on the Network Layer.

How IP Broadcasts are Sent via the Network Layer

Remember how we stated that broadcast addresses are always the highest-most number in an address range? IP broadcasts are no exception! On a network that isn’t subnetted, we can simply place 1’s in place for each bit in the host portion. The result: our very own broadcast address!

Things are still fairly simple: simply replace each host portion with the highest number you can create with 8 bits: 255. Notice that the network portions do not change- just the host portions.

Sadly, this is where things start to get a little trickier: we need to find the broadcast address of a subnetted network.

How to Find the Broadcast Address of a Subnetted Network

We need two things to find the broadcast address of a subnetted network: an IP address, and the subnet mask. The process is simple: find the inverse of the subnet mask. Then take the result, and logically OR it with the IP address to get the broadcast address.

Of course, we can convert the above binary result to decimal and get the broadcast address of 192.168.16.31. If you aren’t familiar with the OR process, it’s rather simple. If there is a 1 in either the IP or subnet field, then the result will always be a 1. (Otherwise, the result is 0)

Now we know how to find the broadcast address and how it works- but what is it used for?

What are Broadcast Addresses used for?

Broadcasts are generally used for several reasons:

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• Address Resolution Protocol (ARP) uses broadcasts to map physical addresses to logical addresses. To build the table of hosts, a device needs to send a broadcast to every other device on the network to essentially find out who is where.
  
  
• Several types of network protocols and services use broadcasts in the same way. Dynamic Host Configuration Protocol (DHCP), for instance, requires that broadcasts be used to dynamically assign an IP address to computers on a network.
  
  
• Routing protocols such as Routing Information Protocol (RIP) use broadcasts to send out “advertisements.” This advertisement is used by routers to map out the topology of a network, so that data can be routed to the appropriate place accordingly. (Interesting enough, this protocol will attempt to find the fasted route through a network to a destination, based on how many “hops” it takes to get from the sender to the receiver.)
  

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Final Points of Interest on Broadcasts

Keep in mind that broadcasts will travel to every single client on a network- at least, until a router is encountered. A router is the only device that can separate a broadcast domain. Logically, this is mandatory for the internet to exist. What do you think would happen if broadcasts were being sent from network to network- all over the internet? (Hint: no more Internet.)

Also make note that broadcast addresses should never be used as host addresses. This can be confused in subnetting, where it isn’t always clear where the host portion starts and ends. The broadcast address is reserved as the highest value- and likewise, no IP address should use a broadcast address or problems will arise.

A properly designed subnet can do wonders for the security and performance of a network. The main idea in subnetting is to divide a network into smaller pieces, which we call subnets. Actually implementing a subnet is typically more difficult than simply using the default subnet mask of 255.255.255.0. This usually means that temporary or smaller networks do not need to be subnetted.

Security sees benefit since the IP addresses of the host computers on each subnet are masked by the network address- which means they are invisible to the outside world. We call this network address translation, or NAT. This same technique helps conserve IP addresses, since all hosts on the subnet essentially just use the network IP address during communication.

A Basic Review on Subnetting

If you’re a little rusty on the basics of subnetting, don’t worry. We’ll cover everything you need to know from beginning to end. First thing first: we need to learn about the IP basics.

The current version of internet protocol, or IP, is IP version 4. This IP version allows four octets of data to represent an IP address. Each octet is considered to be a byte, so there are 8 bits in every octet. Note that in binary form you can see that there are 8 numbers, each one consisting of a bit. Finally, each octet is separated by a period, as shown below.

Each IP address is usually represented in decimal form, as seen above as “192.168.2.1”. However, each IP address is actually used by computers in binary form. You may have noticed a huge flaw in IP version 4: the amount of unique IP addresses is limited! To be exact, only 4,294,967,296 unique IP addresses can be created. This may seem like a large number but keep in mind every single device in the world needs a unique IP address to communicate with one another while online.
The IP version 6 protocol was created for when the transition is needed. Most computers don’t use IPv6 just yet, but in the future it will inevitably be used. (In case you were wondering, IPv6 will support 2^128 unique IP addresses… egad!)

Classes

There are three main types of classifications of IP addresses in IPv4: class A, class B, and class C. There are class D and class E types, but those are for multicasting and private uses, respectively. Each class differs by the number of network and host octets it has. Each network octet is for classifying which network a host is on. More network octets will mean more networks! Likewise, each host octet specifies a host that can be assigned to the network. More host octets means more computers per network.
Each class has a certain range that the first octet can be assigned to. This lets us know to what network class any IP belongs to with ease. Review the diagram below to see a visual diagram.

Now the bad news: you must memorize each range for each class if you hope to pass most network exams. Don’t worry! It’s actually easy- just memorize how we get the numbers, not the numbers themselves! All you have to do is remember n^8 (read as “n” to the eighth power), and how many network portions each class has. Review the diagram below.

One final note before we move on. Notice how we didn’t use the IP address 127 for the class A network- that’s because this is loopback address. We use this for testing configurations on the IP network. Also take note that there are reserved IP addresses, such as those for private networks. These IP addresses will not connect to the internet, which is handy if you just want computers to be connected with each other- and not the whole world.

Subnet Masks

A subnet mask is what we use to assign different amounts of networks and hosts to an IP network. It essentially divides the IP address into two parts: the network and host. This is a trading game- the more hosts you have, the fewer networks you will have. And yet the more networks you have, the fewer hosts you will have. Review the class A default subnet masks as shown below.

The class B network will need to recognize two network portions, and two host portions. This can be seen in the below diagram.

Lastly, we have the class C subnet. It is the most commonly used subnet, so pay special attention to it in the upcoming lecture. You can see a diagram of the default subnet below.

We’ve laid Down the Foundation, Let’s Build the House!

We just reviewed the basics of IP addresses and subnet masks. The bad news is, we usually don’t use the default subnet mask at all when we subnet a network! The good news is, learning how to subnet isn’t too hard. It will, however, take some practice.

An Example of Subnetting a Class C Network

Subnetting varies in difficulty, depending on which class you are subnetting. More often than not, you will need to create a subnet for a class C network. A class C network allows for many networks to be created, but not as many hosts. In fact, you can create a hefty 2,097,152 networks- but only 254 hosts per network are allowed.
Let’s say we are subnetting a school’s network. We need 5 separate networks that have 30 computers on each subnet.
First we calculate how many usable subnets we need. Next we will need to determine how many hosts are required. Both of these values can be calculated with the following equations:
Two Important Equations to Remember:

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• 1. Usable Subnets = (2^n) – 2 , where N = power of bits assigned
• 2. Usable Hosts = (2^n) – 2 , where N = power of bits remaining
  
  
  

Let’s start with usable subnets. Review the diagram below for a visual example.

If you are wondering what the “-2” part of the equation is for, this is how we account for the two addresses in each subnet we can’t use. We will review what these addresses are for more specifically later on. For now, let’s find out what our usable hosts are!

Alright Already! What’s My Subnet Mask?!

Getting your subnet mask at this point is incredibly easy. Simply take all of your network bits, and add them up. Look at the diagram below for a visual guide.

That’s it! You’re done. You have successfully created a subnet mask that can be used on the school’s network. Keep in mind that every computer must have the subnet mask set in order for them to be on the same network. Also note that since we are using a class C network, the first three octets will always be 255. When subnetting other classes, be sure to keep the network portions in mind.

Closing Comments

Subnetting may not be fun, but it is required for students to know on networking exams. That means you should stay away from subnet calculators until you have grasped the full concept of how to do it yourself. These calculators should only be used as a time saving tool, not a learning tool or way to cheat on homework.
With enough practice, subnetting will become much easier. Class A and Class B networks are a bit trickier, but follow the same example as shown above and it should be quite easy to accomplish.

With Windows 7 due out later this month, many of you are no doubt counting the days until release. I've played with both the beta and RC of Microsoft's latest OS, and quite honestly, I liked what I saw. If this had come out in 2006 when 'Longhorn' was promised, I have no doubt that I would not have switched to Linux (at least not yet).

However, that's not how events played out. What really happened was 'Longhorn' became Vista, and it didn't make it out the door until 2007. It arrived late, buggy, irritating (UAC), overpriced, underwhelming, confusing (licensing), and in some cases, incompatible. Now, almost three years later, and almost five since Longhorn's initially-planned release, Microsoft is releasing the OS they should have launched several years ago. Unfortunately, Windows 7 is also overpriced (slightly less so than Vista), and even more confusing.

But first, let's go over what Microsoft did right. Windows 7 is going to launch when the company said it will launch. Because of a long beta and RC testing phase, 7 is not going to be as buggy as Vista was when it debuted. Microsoft has taken the UAC down a notch. It has also come down on the price a little. The highest edition of 7 (Ultimate) is fifty percent more expensive than the highest edition of XP (Pro). This is opposed to 100% more expensive (Vista Ultimate versus XP Pro). But fair enough, the price did drop somewhat.

Underwhelming, 7 is not. In terms of its user interface, Vista was pretty much XP with a reorganized Start Menu and a black taskbar. Flip 3D was basically nothing more than a choppy gimmick (though the thumbnail previews of windows within the taskbar are pretty sweet; Windows 7 kept them, and I use them in Linux). Windows 7 actually succeeds in terms of a being a unified vision that pays tribute to the brand. Everything is made of glass in 7. Vista began this trend with the transparent glass window borders and the overlaid faux-reflection texture. But 7 really takes the use of transparent glass and reflections to the extreme. The window borders, menus, some applications, and even the taskbar and start menu are all made of glass. New tricks include being able to make all windows transparent to see the desktop. As a total package, Windows 7 has what I consider to be the first true Windows theme.

Finally, we're left with how Microsoft figured out how to solve its backward-compatibility issues.

With the introduction of XP Mode (XPM), Windows 7 will not fall victim to the nightmare of incompatibilities suffered by early-adopters of Vista. XPM is a fully-licensed copy of Windows XP Service Pack 3 running in a VirtualPC Virtual Machine (VM). In many cases XPM is the clincher that holdouts needed in order to finally upgrade. Unfortunately, the confusion created by the Windows 7 licensing scheme has all but ruined their compatibility fix.

XPM is only included in Windows 7 Professional and Ultimate. If you want a full retail boxed copy of Windows 7 with XPM, you're going to have to fork over $300 for Professional, or $320 for Ultimate. If you already own a copy of Windows XP or Vista, you can pay $200 for the upgrade to Professional, or $220 for Ultimate. Let that sink in for a minute.

That's right, Windows 7 Home Premium (and below) does not have XPM. Most systems sold by retailers come with a version of Windows completely lacking XPM. Wait, it gets better. Thanks to Microsoft's ingenious Windows Anytime Upgrade, consumers who bought a new PC with Windows 7 Home Premium can upgrade to Professional for $90 or Ultimate for $140. If you were sold Home Basic or Starter edition, you'll have to first upgrade to Home Premium for $80. Like I said, 'ingenious.' One way or another, you are probably going to have to pay Microsoft some amount of money if you want XPM...

...or not. If you're open to using Linux , you too can have a fast and secure next-gen OS with full XP compatibility, all for free!

begins with the assumption that you've already installed Linux on your system. If you need help with the installation process, go here for a refresher. I do not assume that you have any Linux knowledge, but you should be comfortable with PCs in general.

Test System Specs:

Operating System	64-bit Ubuntu 9.04 “Jaunty Jackalope”
Processor	2.0 GHz AMD Athlon 64 X2
Motherboard	Biostar NF61S-M2 TE
Memory	4GB DDR2-800MHz
Graphics	Nvidia GeForce 6100; integrated graphics, 128MB shared
Storage	250GB SATA 3 Gb/s, 7,200 RPM

The first step to getting your very own XP Mode in Linux is to install virtual machine software. Since the point of this article is saving money, we're going with Sun Microsystem's free VirtualBox as our virtualization software. Click here and choose the appropriate .deb or .rpm file for your Linux distribution. I am using the 64-bit version of Ubuntu 9.04, so I'll need to click the AMD64 link next to Ubuntu 9.04 (“Jaunty Jackeloupe”). You can choose to either run or save the file.

Though it is free, this app is not open-source. This is the version of VirtualBox that contains proprietary code. If you only want open-source software on your system, you can use VirtualBox OSE (Open-Source Edition) instead. You can get VirtualBox OSE from Add/Remove in the Applications menu. Click here if you need a refresher on installing software in Ubuntu via a package manager. You can follow this guide to setup the OSE version, for the most part. Some of the steps will deviate slightly. Also, the screenshots may not represent exactly what is on your screen.

If you chose to save the file, double-click it when downloading completes. Click Install Package, then enter your password when prompted. When the Debconf window opens, just click Forward to continue installation. After the application finishes installing, click Close, and then exit the installer by closing the window. If you wish, you can now delete the .deb or .rpm by right-clicking on it and selecting Move to Trash.

Remember the Debconfig window? Now we have to add you to the list of authorized users in the “vboxusers” group so that any USB devices will work in the Windows XP VM. It's not just your Windows apps that you'll be able to use in the VM; devices too! Now, go to System/Administration/UsersandGroups.

In the user list highlight your user name by clicking on it, then click Unlock. In the screenshot, my user name is Adam Overa.

When prompted, enter your password and then click Authenticate. Now click Manage Groups. Scroll down until you see the group vboxusers, click it, then click Properties.

You should see the user list with check-boxes next to the user name of each user on your system. Check the box next to your user name and click OK. Now click Close, and then Close again. Now we need to log out, or restart for these changes to take effect. Click on your user name on the far right of the upper panel. Select Log Out to go to the Ubuntu login screen, or Restart to reboot.

When you get back to the Ubuntu desktop you can now open VirtualBox viaApplications/SystemTools/SunVirtualBox. Since we are using the free version of Sun VirtualBox, and not the free and open-source version, we need to agree to the license agreement. To do this, scroll all the way down and then click I Agree.

Next, the VirtualBox Registration Dialog window should open. If you already have a Sun Online account, enter your email and password and click Register. If not, you can enter your information and click Register. Alternatively, you can also just click Cancel to continue. Once VirtualBox opens, click on the New button in the navigation bar. This opens the Create New Virtual Machine wizard. Click Next.

In the Name field, enter a name for your new virtual machine. If you plan on having several VMs, name each VM descriptively to avoid confusion (such as “Windows XP SP3 32-bit”). You could also name the VM for its intended purpose, such as “Gaming,” “MS Office,” or “Compatibility Testing.” Under OS Type, you can choose the operating system and version. Since VirtualBox defaults to Microsoft Windows in the OperatingSystem field and Windows XP in the Version field, we can leave it alone and click Next.

Now we must decide how much system memory we want to allocate to the virtual machine. In this respect, the VM is much like a real system; the more memory, the better. You can allocate up to half of your system's RAM to the VM. My test system has 4GB, so I'm going to give 1GB to the Windows XP VM. This will leave the host OS (Ubuntu) with 3GB when XP is running. After you have decided how much RAM to give to your VM, click Next.

Since this is the first time you're running VirtualBox, there won't be any virtual hard disks to chose from. Therefore, we must select Create new hard disk, and then click Next. This opens the Create New Virtual Disk wizard. Click Next again.

On this screen, we are presented with the choice between Dynamically expanding storage and Fixed-size storage. The difference is that Dynamically expanding storage will only take up the amount of space usedby data in the VM. Fixed-size storage immediately takes up the entire size of the virtual disk. With either option, you will need to specify the size of the virtual disk after clicking Next.

The Location field on this page should already be indicating the name that you gave the VM earlier. Using either the text box or the slider, you can specify the size that you want your virtual hard disk to be. Remember, if you chose Fixed-size storage, your real hard disk will lose whatever amount you decide here. If you chose Dynamically expanding storage, this is the maximum amount of space your virtual hard disk will be allowed to consume. I'm happy with the default size of 10.00GB, but you can specify any size that works for you. Click Next.

The Summary Screen will display the type and size of your virtual hard disk as well as it's location on your real hard drive. Verify that the options are correct, and perhaps make note of the virtual disk's location. This is a good idea in case you want to backup, or even take your virtual hard disks with you. When satisfied, click Finish. The more space you've given to Fixed-size storage, the longer this will take. After your virtual hard disk is created, that wizard will close and another summary screen will display the Name,OS Type, Base Memory, and Boot Hard Disk that you selected for your new virtual machine. Verify the information and then click Finish.

Now that we have created a VM (including the virtual hard disk) for Windows XP, we need to tweak some settings. You should be back to the main VirtualBox window with your new VM highlighted. Click the Settingsbutton in the navigation bar to open the settings window for the XP VM.

Zoom

You'll now see the Basic tab of the General page. Here, you can change the Name, Operating System, andVersion. We just set those options when we created the VM, so ignore this page and open the System page in the left pane.

Zoom

Now we're on the Motherboard tab, which houses options for adjusting the VM's Base Memory, Boot Order, and Extended Features. We do not need to change any of these options, so click the Processor tab. If you're lucky enough to have a sickening amount of system RAM (enough to give your VM 4GB or more), you will need to check the box next to Enable PAE/NX in order for a 32-bit OS on your VM to address that much. Click on the Acceleration tab to continue.

If your CPU has hardware-accelerated virtualization capabilities, you will want to check the box next toEnable VT-x/AMD-V so that the VM can utilize them to boost performance. If your CPU has nested paging capabilities, check the box next to Enable Nested Paging for another performance boost. If your CPU doesn't have either of these, the selections will be grayed out.

Click the Display option so that we can adjust the Video Memory Size. My PC has up to 128MB of video memory that I can allocate to the VM. You can choose whatever size that you think you'll need. A good rule of thumb is that the more high-resolution gaming you do, the more video memory you'll want to allocate. Also click on the checkbox next to Enable 3D Acceleration if you anticipate any gaming.

Next, click on the CD/DVD-ROM page in the left pane. We need to check the box next to Mount CD/DVD-ROM. Now, check the box next to Host CD/DVD Drive. If you have multiple optical drives, select the one you will use to install Windows XP from the drop-down menu. If you have your Windows XP disc handy, insert it into your optical drive of choice. If your file manager automatically opens after inserting the disc, simply close it.

Before we're ready to install XP, we need to set up a folder to share files between the Linux host OS and the XP guest OS. Click the Shared Folders page in the left pane. First, click on the Add button on the far right (blue folder with green plus sign) to open the Add Share window. Next, click on the drop-down menu next to the Folder Path field, then choose Other. Now, find or create a folder in your Ubuntu file tree where you want data to be shared with your XP installation. I chose the Public folder in my Home directory located at /home/adam/Public. Click Open, and then OK. Wherever you create that shared folder, make sure you remember where it is. Click OK to finish tweaking the Windows XP VM's settings.

Now that we are done configuring the VM's settings and the XP CD is in your optical drive, we can boot the VM for the first time. We are back to the VirtualBox main window and your Windows XP VM should be highlighted. Click the Start button in the navigation bar. A new window will open for the XP virtual machine. After a few seconds of nothing, and maybe a window resize or two, the familiar blue screen of Windows' pre-installation will appear. When you first press a key with the VM window selected or click the mouse inside of it, a Keyboard/Mouse capture pop-up window may appear. You can decide to read it or not before you close it; in a few pages, you won't need to use the Host key anyway.

From here, you can install Windows XP as you normally would. In a nutshell: Enter, F8, Enter, Enter, Restart. As long as the XP VM window is the currently selected window, any keystrokes will register in the VM and not in your host OS. When the VM reboots, you should be in the XP graphical installation that we all know and love.

When the loading stops, the Regional and Language Options need to be dealt with. To use your mouse in the VM, left-click once anywhere inside of the VM window. The mouse is now being used by the VM and not the host OS. Also, its movements are restricted to inside the VM window. The little mouse icon directly to the left of Right Ctrl has been filled with color to indicate the mouse is bound to the VM. Press the right Ctrlkey (that is, the Ctrl key on the right-hand side of your keyboard) in order to unbind the mouse and return it to the host OS.

Now that you know how the keyboard and mouse interact with the VM, go ahead and finish the graphical installation of XP. Basically: Next, enter name, Next, enter product key, Next, Next, time zone, Next, Next,workgroup name, Next. After another pause, the graphical installer will perform another reboot. Do Not"press any key..." to boot from CD-ROM if prompted. That will only result in going back to the beginning of the installation.

The familiar Windows XP loading screen should be showing up. If you are asked to resize the screen, clickOK and then Yes. If all went well, the VM's window should become larger. If not, don't worry, we'll be changing it later anyway.

Depending on your edition of Windows XP and how old the CD is, another phase of the graphical installer may appear. Follow it until you get to a working desktop. There should be some music, and the little help icon in the lower-right should also be making sounds. Note: If you don't hear any sound, or if the sound comes out garbled, you'll need to tweak your VM audio settings later. Finish the graphical installation first.

Whenever you do get to your first working desktop screen, as with any other Windows installation, update the operating system before proceeding!

Installing Guest Additions

With Windows XP updated and booted, it's time to install some VirtualBox optimizations. Unbind the mouse from the VM by pressing the right Ctrl key. Click on Devices in the menubar of XP's VM window, then clickInstall Guest Additions.

The Sun VirtualBox Guest Additions setup screen should open. Rebind the mouse to the VM by left-clicking anywhere on the Windows desktop. Click Next, I Agree, and then Next again. Check the box next toDirect3D Support (Experimental) if you plan on utilizing DirectX 3D graphics. Click Install to begin copying the Guest Additions files to your VM. When Guest Additions is done installing, click Finish to reboot.

After Windows has rebooted and you're back to a workable desktop, a VirtualBox icon will be in the notification area of the taskbar. If you had previously resized the desktop's resolution, it may have reverted back. Also notice that your mouse is now able to move between the VM and host OS without clicking or using the Ctrl key. This is called Mouse Integration and is part of Guest Additions. It can be turned on and off from Machine in the menubar, or by pressing right-Ctrl+I.

Sharing Files

Remember the shared folder we designated when we tweaked XP's VM settings? You're going to need it now. Navigate to the shared folder in your Linux file manager (mine was the Public folder in my Home directory, /home/adam/Public). This is where you'll put files from Linux (the host OS) that you want to share with Windows XP (the guest OS). This is also where you go to receive files from XP to Linux.

To make files from Windows XP available to the Linux host, or to receive files from Linux in XP, you need to first boot up the XP VM. In this step, the sequence must be followed to the letter. This is very easy to get wrong, and a misstep will result in you starting over.

Follow the mouse pointer in the screenshot below for easy reference. From the Start Menu, open My Computer, then click My Network Places in the Other Places sidebar. Next, click View workgroup computersin the Network Tasks sidebar. Now, click on Microsoft Windows Network in the Other Places sidebar. Click on Entire Network again, in the Other Places sidebar. Now, there should be an entry for VirtualBox Shared Folders in the window. Double-click it.

Your shared folder should be there, listed as \\VBOXSVR\"folder name.” For example, mine is\\VBOXSVR\Public. Since it's such a hassle to go through the XP file manager's sidebar to get here, it's a good idea to put the shared folder in your Favorites. Just click Favorites/Add to Favorites when you're inVirtualBox Shared Folders. From now on, you can get to the VirtualBox Shared Folders directory fromFavorites in Windows Explorer.

Now you'll be able to easily transfer files between the Linux host OS and the XP guest OS.