Day 22
Help in Troubleshooting with:
Understanding data loss
Understanding Error Messages
A Plus Test Continued
LAN is short for Local Area Network and they are used to transfer data and share resources between systems that are connected together using a network adapter.
So what exactly is a LAN, you ask? In simple terms, a LAN is basically a bunch of computers networked together in close proximity to each other. A LAN has many uses, Sharing large files such as MP3s, gaming, sharing resources such as a printer or CD-RW.
To start we're only going to cover Ethernet and Fast Ethernet on this day.
Ethernet is easily the simplest and cheapest option. It runs at 10 Megabits per second (Mbps), or roughly 1.2 Megabytes per second, which is more than sufficient for a small LAN.
10BaseT, also known as RJ45 twisted pair is the cable that we use in an Ethernet setup.
Fast Ethernet (100BaseT) is the current popular standard. It has a fat 100Mbps pipe, ten times faster that plain vanilla Ethernet.
You can have just two computers on a very simple network, using a "crossover cable"
Here is a diagram. Note: No hub is needed in this setup. The drawback is that this setup is limited to just two computers.
What about a real LAN? Basically, each computer on the network runs a length of cable to a central hub, which functions to pass the network traffic through each computer. Here is a diagram.
Here is a way to set up a LAN
Each system on the LAN will need a network interface card, or "NIC," installed. The NIC is the card that goes into each computer to make it network ready.
3com and D-Link cards tend to be best and give you fewer headaches.
Now you need a hub. The speed of the hub determines the speed of the network.
Hubs come in three flavors: 10BaseT, 100BaseT, or 10/100BaseT autosensing. 10BaseT hubs are for 10Mbps networks, and are the cheapest ones out there. They are only compatible with 10BaseT or 10/100BaseT cards. 100BaseT hubs are for 100Mbps networks, and they are only compatible with 100BaseT or 10/100BaseT cards. I recommend 10/100 autosensing hubs, as they are compatible with 10BaseT, 100BaseT, and 10/100BaseT network cards.
Hubs have ports, which allow you to connect your PCs. So buy a hub that has enough ports to fit all of your PCs.
Cable is needed, unless
you are running a wireless network. You may buy these CAT 5 cables premade
or crimp them yourself. To do it yourself, you will need RJ-45 Crimp &
Cutter tool, like the one below.
Here are the steps in creating a crossover cable for two PCs.
1. Determine the distance between the two computers or device and plug, then add 14 inches to this length.
2. Cut a piece of standard Cat5 unshielded twisted-pair cable to the length you need.
3. Strip 2 inches of the jacket off one end of the cable. The Crimp tool should do this cut nicely.
4. Hold the 4 pairs of twisted cables tightly where the jacket was cut away, and then reorganize the pairs into the 568-B standard, as seen here...The pairs should be orange pair, green pair, blue pair, brown pair.
568-B
5. Now hold the jacket and cable in one hand and untwist a short length of the green and blue pairs and reorder them to look like the 568-B diagram, Untwist the rest and order them as the color scheme.
6. Flatten, straighten, and line up the wires. Trim them in a straight line to within 1/2 inch from the edge of the jacket. The wires should be in proper order.Do be sure that this length is small, because this is a source of electrical noise
7. Place a RJ45 plug on the end of the cable, with the prong on the underside and the orange pair at the top of the connector.
8. Push the plug onto the wires until you can see the copper ends of the wires through the end of the plug. Check the order. The jacket needs to be inside the plug. Now crimp the plug hard enough to force the contacts through the insulation on the wires.
9. Now repeat steps 3 to 8 to terminate the other end of the cable. Use the 568-A standard to do this.
568-A
This will create a crossover cable, to be used between two computers.
To make a cable that works with a PC to HUB, then use the 568-A standard on BOTH ends.
Once you have the hub and power supply connected, all that is left is to connect the cabling. 10/100BaseT networks require "Category 5 cabling" with RJ45 jacks, often referred to as Cat5 cable. One end of the Cat5 goes into the network card, and the other end plugs into a free port on the hub.
Now- all that's left is to power up the systems, let Windows Plug and Play find everything, and configure the IPX and TCP/IP protocols.
In most cases, Windows will detect the new NIC and launch the Add New Hardware Wizard. At this point, Windows will either ask for the Win98 CD or more commonly, ask for a driver disk from the manufacturer. When Windows asks if you have the driver files, insert the NIC installation disk into your CD-ROM drive.
After rebooting your system, check the Device Manager in the System window of the Control Panel. Make sure there isn't a yellow exclamation symbol next to your network card. If there is a symbol, there's probably a resource conflict between the NIC and another system component. Try changing the resource settings of the NIC if this happens, then double click the device and check the Device Status box in the General tab. Any system resource conflicts will be listed here. If you are experiencing a problem, click on the Resources tab and view the Conflicting device list. You should then be able to select the "Set Configuration Manually" button and choose a new I/O range or IRQ to free the conflict. "
After everything is installed and working, you will need to setup the windows 98 peer to peer networking. This is the standard Windows setup for a low security network.
Go into the Control Panel and select the "Network Icon. This will bring up your network properties screen.
Your network card should appear in the list of installed network components. If it's not there, the network card isn't installed properly. Our generic network card appears as a NE2000 Compatible. Your network card will probably appear under a different name.
Check to see if Windows already installed TCP/IP and IPX/SPX for the network card. If they are already installed, you should see something like "TCP/IP -> NE2000 Compatible" and "IPX/SPX-compatible Protocol -> NE2000 Compatible"
TCP/IP Setup
Install TCP/IP first. Go to the network menu and highlight your network card.
Now, click on the add button. That will take you to the "Select Network
Component Type" window. Highlight protocol, then click add.
"Select Network Protocol" window will now open. Go down the left side, and select "Microsoft" from the list of manufacturers on the left. Then select "TCP/IP" from the list of Network Protocols on the right. Click OK. That will return you to the Network window, and you should now see "TCP/IP -> NE2000 Compatible" in the list of installed network components.
Now repeat the above steps, but choose "IPX/SPX-compatible Protocol" instead of "TCP/IP" in the "Select Network Protocol" window. Now you should have a new "IPX/SPX-compatible Protocol -> NE2000 Compatible" line in the list of installed components.
Now repeat the above
steps again, but choose "NetBEUI" in the "Select Network Protocol"
window. NetBEUI will make Microsoft file and printer sharing much better.
After installing NetBEUI, go to its properties window, and check the "
Set this protocol to be the default protocol" in the advanced tab. Don't
install NetBEUI if you aren't going to use Microsoft file and printer sharing.
Data loss occurs when a user can no longer access his or her system. Unfortunately, in more than 75% of cases, the victims might have recovered the data if the user had known what to do. Data loss can be disastrous to a business.
Causes of data loss
According to a study conducted by engineers at Ontrack Data International, Inc., a data recovery company, the five major causes of data loss are as follows:
w hardware or system malfunction
w human error
w software program malfunction
w viruses
w natural disasters
Almost half of all data lost is the result of hardware or system malfunctions. An electrical failure, a head or media crash, or controller failure often causes hardware or system malfunctions.
To determine whether your data loss is the result of a hardware problem, look for the following symptoms:
ü error messages indicating that your system does not recognize the hardware
ü data disappearing suddenly
ü a scraping sound when you try to access the hard drive
ü the hard drive does not spin
Data loss caused by hardware or system malfunctions is sometimes recoverable, but you should stop using the hard drive immediately. If you are sure that the drive has suffered damage, do not attempt to open it unless you are in a clean room.
If you have suffered data loss as the result of a hardware or system failure, do not attempt to use a software recovery program. These programs can cause further damage if the hardware is not functioning properly. Instead, take the drive to a data recovery company.
Although you cannot always prevent system or hardware malfunctions, you can take precautions to ensure that you don’t do anything to cause a malfunction. For example, place computers in a dry area and avoid dust, tobacco smoke, and direct sunlight. You always should use an uninterruptible power supply (Universal Power Supplies) to avoid electrical power surges, and do not remove a hard drive and shake it or disturb the platters inside the cover.
The second most frequent reason for data loss, the culprit in 32% of all data losses, is human error. This often takes the form of accidentally deleted data, a dropped computer , or a mistake on the part of a network administrator.
The only real symptom of data loss caused by human error is that your data suddenly disappears.
You can attempt to recover data several ways, if it is lost due to human error. These methods are not always successful, but your chances are better than in the case of a hardware or system failure. Try these following steps:
ü Use the undelete feature included with the operating system.
ü Do not allow access to your data to anyone who does not know how to manage it.
ü Contact a recovery service for professional recovery.
ü If the data loss is the result of dropping the computer, follow the steps you would to recover from a hardware or system malfunction.
The best way to prevent this type of data loss is always to have a backup. In addition, you should install new software or hardware only after backing up your system. To prevent dropping the computer, do not move it unnecessarily and never while it is in operation.
Although viruses are growing more common and more numerous all the time, they account for only about 7% of the total lost data. However, you can prevent and recover from virus-inflicted data losses.
To determine whether your data loss is the result of a virus, look for these symptoms:
ü A message appears on your screen.
ü Your screen is blank.
ü You have unpredictable results when attempting to access your data.
ü You get error messages indicating that the files are no longer found or that device is no longer available.
Before attempting to recover the lost data, contact an anti-virus software vendor. Their experts are available to tell you whether your data will be safe when you remove the virus.
See additional information about viruses in the handout sheet on Understanding Computer Viruses.
The most important way to prevent data loss by virus is to install and use anti-virus software. You must check any incoming software for viruses as well as any attachments you receive. Even using anti-virus software is not a guarantee that you will avoid a virus, however. Avoid opening e-mail attachments from people you do not know, and purchase software only from reputable companies.
Although they are responsible for only 3% of all lost data, natural disasters such as floods, fires, earthquakes, hurricanes, power surges, and lightning strikes do cause data loss. Of course, if you live in an area that is more susceptible to floods, earthquakes, and other natural disasters, your odds increase.
It is usually evident whether your data loss was caused by a natural disaster such as a fire, earthquake, or flood, but determining data lost due to a lightning strike or power surge is more difficult. The only real symptom in those cases is that the data is no longer accessible. There may be damage to other parts of your system, causing a more complete malfunction than mere data loss. In that case, follow the guidelines for recovering data lost due to a system or hardware malfunction. In other instances, remember the following warnings:
ü You should never use equipment that has been exposed to water, extreme heat, or soot; turn the system over to a data recovery system.
ü You must not operate a system that is obviously damaged or that you believe has damage; you could permanently destroy the data and make any type of recovery impossible.
Because you cannot prevent natural disasters, the only data loss prevention is to use safeguards to ensure that you do not lose all data in case of a disaster. Always use a UPS and store backup copies of your data at an offsite location. If you live or work in a flood plain, it is even more important to back up data regularly and store it offsite.
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Message: Abort, Retry, Fail
Solution:
There is a problem with the diskette. Ensure that you entered the correct drive
letter in the command and you inserted the diskette properly in the drive. You
might also get this message if you are trying to use an unformatted floppy
disk.
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Message: Bad Command or File Name
Solution:
Check the file location and ensure that the path name is correct. You should
also ensure that your version of DOS recognizes the command.
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Message: Bad or Missing Command Interpreter
Solution:
Boot the system from a system diskette that contains the COMMAND.COM
file, copy the
contents to the root directory of your hard drive, and reboot. Then you should
ensure that the SHELL command is in your CONFIG.SYS file.
¨
Message: Drive A: Does Not Exist
Solution:
This error occurs when the A floppy
drive cannot read the disk. This usually is the result of a dirty or defective
floppy drive. You should try cleaning your drive. If the drive continues to
malfunction, the drive or the controller is probably defective and you need to
have it repaired or replaced.
¨
Message: File Cannot Be Copied Onto Itself
Solution:
This message usually occurs when you forget to enter the complete command. If
you use the COPY command and do not specify a destination, DOS attempts to copy
the file to the current location. DOS will not make a copy of a file in the
same directory where the original file exists.
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Message: Incorrect Dos Version
Solution:
This error occurs when you upgrade your MS-DOS version without removing all
files from the old version. You can re-install DOS to solve this problem.
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Message: Insert System Disk
Solution:
The operating system needs a system disk from which to load the operating
system.
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Message: Insufficient Memory
Solution:
This errors occurs when you do not have enough memory available to complete a
command. You can usually remove terminate-and-stay-resident (TSR) programs and
run the command again.
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Message: Invalid Parameter
Solution:
Check the command and re-enter it exactly as shown. Also verify that you are
not using a parameter that is not used in the program you are using.
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Message: Non-System Disk or Disk Error. Replace and Strike Any Key
Solution:
This error usually occurs when you reboot the system with a floppy diskette in
the drive. The PC examines the floppy disk first for the MS-DOS system. If the
diskette in the drive does not contain system files, you receive the error
message. Remove the diskette and press any of the keys on your keyboard to
continue the boot process.
¨
Message: Out of Memory
Solution:
This message indicates that you do not have enough system memory to complete an
operation. You can add additional RAM to your system, or try running a memory
optimization program, such as MemMaker with DOS 6.x.
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Message: Read Error
Solution:
This error indicates an error on your hard drive, usually as a result of hard
drive damage. Run ScanDisk to find the error and attempt to save the data
stored at that location.
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Message: Stack Overflow – System Halted
Solution:
This is an internal error and you need to reboot your system.
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Message: Syntax Error
Solution:
This message indicates a typing error or incorrect use of a command.
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Message: Too Many Open Files
Solution:
This common DOS error indicates there are too many open files. This can include
internal files within a single application. You should increase the number of
files indicated in the CONFIG.SYS file, then restart the computer.
¨ Message:
Write-Protect Error
Solution:
You get this message when you attempt to alter a protected diskette. Before you
remove the write-protection, verify that you are using the correct disk.
Resources:
http://fp1.centuryinter.net/eotw/index.html
http://www.open.org/~bilbran/dun.htm
Errors:
http://www.learnthenet.com/english/html/96error.htm
http://www.brown.edu/Departments/Taubman_Center/errormsg.html
FATAL ERRORS:
http://www.springfieldtech.com/how_do/Fatal_error.htm
Do a search under
“fatal error” on the ‘Net to find more information.
