Servicing Networks and Network Computers

Servicing Networks and Network Computers

We're going to examine what is necessary to work on a network computer system. Network PCs require different care and consideration to avoid damage to the computer and the network, as well as avoiding network downtime. You can cripple a network by working on a PC without taking the proper steps, so examine these carefully.

Identification

The first task you must face is identifying a networked PC. The easiest way is to look for one of the three basic formats of cabling leading into the back of the computer; Coaxial, Twisted Pair, and Fiber-Optic. If one of these cables is running to the back of the PC, you are pretty much guaranteed it's a networked PC.

Just because the cable isn't there doesn't mean the PC isn't networked. Look for signs of a Network Interface Card port on the pack of the computer. It's possible the computer has already been unplugged from the network. In fact, it's possible that's the problem. If you see a NIC and no cable, ask if the computer is supposed to be networked.

If you don't see signs of a network cable or a NIC, you can be pretty sure the computer isn't networked. You require both to network with, and the absence of both is a sure sign that the computer is a stand-alone system. Just in case the problem appears to be of a network nature, it never hurts to ask.

Troubleshooting Network PCs

The first rule of troubleshooting Network PCs is the same as with any computer system; Look for the obvious. You'd be surprised how many times people kick a switch with their foot or pull a cable out of it's socket and never realize it. Before you troubleshoot ANY PC, do a quick look to make sure it isn't something simple. This also gives you time to look at what equipment is in the computer and how it is connected to the network.

If it's a network-specific problem, check to see whether you're connected to the network or not. This is done by attempting to open a network folder or drive. If you double-click My Network Places and you see other computers on the network, you know the computer is logged in. If you don't, you must attempt to find out why. (We'll cover more on this in a bit)

If the problem is non-network related, you should take a couple steps before attempting to service the PC. First, back up the files on the PC. (Again, you should be doing this anyways) Secondly, examine the network structure before attempting to make changes. If you remove the cable from a bus or ring topology, you bring down the whole network. Determine what format of network you're dealing with, and decide your action from there.

If you must disconnect a computer from a Bus or Ring network, try to keep the cable plugged into the NIC. Although the computer is not functioning on the network, the network doesn't fail. Star networks don't care, so feel free to unplug them. (When the computer is turned off of course.) If you have to take down a network, make sure you tell someone first, and set a realistic time table for how long they will be without network services.

If the trouble with the PC is network related and you can't log on to the network, more skill is required.

Look for kinks, breaks, and folds in the cable leading up to the network. Broken cables can isolate PC's on a network, and can often lead to a total network failure.
Look at the Protocols that have been installed on the PC, and then look at other PC's in the network. If you're missing a network Protocol, try re-installing it.
Make sure the User Account on the computer was logged in to. If someone hit the Escape (ESC) key instead of typing in the password, the computer won't log on to the network. Also make sure the user account is present on the server.
Try plugging in a different NIC. A defective NIC can be a pain to troubleshoot, and often won't show in the in the device manager as defective.

If after those steps you still can't log on, I suggest asking a certified network technician for advice. They have methods of determining problems quicker than the standard "Hunt and Peck" method, and will say you time and your customers money. Read up about Frame Types for IPX networks, permissions for NT networks, and other networking issues in our MCSE tutorials for hints as to how to solve networking problems.

A Quick Lesson In TCP/IP

Because the Internet has become so widespread, learning the basics of the TCP/IP protocol is imperative for any computer technician. Therefore, here is a quick lesson in the Transmission Control Protocol/Internet Protocol.

Terminology

TCP/IP - Transmission Control Protocol/Internet Protocol - The primary protocol used on the Internet. TCP controls how packets are broken down to be transmitted on the Internet, and IP states how individual nodes are addressed and re-assembles the packets on the receiving end.

IP Address - TCP/IP uses a numerical address to distinguish nodes. This address consists of 4 8-bit numbers separated by decimals. For example, 123.92.145.17 is a valid IP address. The first 2 sets of numbers are the network identification portion of the address. The second 2 sets are the host identification portion. Computers on a network will share the same network identifier, but must have unique host identifiers.

Domains - A domain is a distinct network in a TCP/IP system. All nodes in a domain share IP addressing properties and security systems. They also share a common domain name. For example, all computers on a network assigned to a specific IP can be found by a simple <name>.com system. ABS-CBN.com is a domain name, and all computers associated with ABS-CBN.com networks share the same IP network identification and structure. Domain names are used because they are easier to remember than the IP number.

HTML - Hypertext Markup Language - The basic format used to present information for web browsers on the internet.

HTTP - Hypertext Transfer Protocol - The protocol used to transfer HTML documents on the Internet.

IP Addresses

As we stated before, IP addresses are always 4 sets of 8-bit decimal numbers. This makes IP addresses 32-bit. Each 8-bit segment is called an octet, and has a maximum value of 255. This makes a maximum total number of IP addresses of 4,294,967,296 on the Internet. Although this may seem like a large number, it is not. (IPv6 will be released shortly that will deal with this problem. It has a maximum number of IP addresses in the trillions.)

IP addresses can be assigned in two different ways. Static IP addresses are addressed to a node permanently. Dynamic IP addresses change every time a node logs on to a network. Static IP addresses are necessary for computer that always must be associated with a single IP address, such as servers. Dynamic addressing is used for nodes that don't require their IP address to always remain the same, such as workstations. By mixing Static and Dynamic addressing, you avoid problems with running out of IP addresses while maintaining the structure of the Internet. Dynamic addresses is performed by a Dynamic Host Control Protocol Server, or DHCP server.

DNS

For large networks, changes in the domain structure can confuse network users. If a domain switches IP addresses or a new computer is added, these changes must be shown to all the computers on the network. This is done through a Domain Name Service, or DNS server. A DNS server keeps track of all the IP addresses on a network, or on the Internet. When a person types in a domain name to access, the DNS server examines it's files for the location and routes the request to the right area. This allows changes in the network or the Internet to be noticed by all the computers on the network without having to tell each individual computer. It also allows you to type in a domain name.

WINS

Windows Internet Naming Service operates the same as DNS, but with a couple differences. First off, WINS is only functional on Windows networks, and can't be used by UNIX or OS2 systems. Secondly, it keeps track of Dynamically Assigned IP addresses as well as Static. This means you can find more computers easier, but only on Microsoft networks.