Network+ Certification (Outline) - Chapter 15: Installing a network

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Chapter summary: External unshielded twisted pair (UTP) cable installations use prefabricated cables to connect computers directly to hubs; internal cable installations use bulk cable, which you pull through walls, ceilings, or floors; to connect two computers without a hub, you must use a crossover cable connection, which reverses the transmit and receive signals;...

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Nội dung Text: Network+ Certification (Outline) - Chapter 15: Installing a network

Chapter 15, Installing a Network |1| Chapter Overview A. Pulling Cable B. Making Connections Chapter 15, Lesson 1 Pulling Cable 1. External Installations A. Installing network cable is often called “pulling cable.” 1. The process often involves threading one end of a cable through a wall or ceiling and then pulling the rest of the cable through from the other end. |2| B. An external installation is one in which you use prefabricated UTP cables and run them from each computer to the hub. 1. You do not have to run cables through walls or ceilings, attach connectors to bulk cable, or purchase additional hardware, such as wall plates and patch panels. C. Advantage of external installations 1. External installations are portable; you can coil up the cables and take them with you if you have to move the network. D. Disadvantages 1. Cables are often visible. 2. Obstacles between the pieces of network equipment can make running the cable difficult. |3| E. External installation procedure 1. Select the locations for the computers (and other network-connected devices, such as printers) and the hub. a. The hub should be in a central location relative to the computers, both to keep your cable lengths to a minimum and to avoid having too many cables running along the same route. 2. Plan the exact route for each cable from the computer (or other device) to the hub. a. Examine all of the obstacles on each route, such as furniture, doorways, and walls. b. Plan how you will run your cables around or through them. 3. Measure each route from the computer to the hub. a. Take the entire path of the cable into account, including vertical runs around doorways, paths through walls, and other obstacles. b. Leave at least a few extra yards of slack to compensate for unforeseen obstacles and adjustments in the location of the computer or hub. 4. Buy prefabricated cables of the appropriate lengths (and possibly colors) for each run.
a. If you are installing UTP cable, make sure that all of the cables you purchase are rated at least Category 5. b. It is a good idea to use molded boots on the cable connectors to protect them from damage. 5. Lay out the cable loosely for each cable run without connecting them to the equipment or securing them to the walls. a. Be sure to leave enough slack to reach around doorways or other obstacles and at each end. (1) Leaving slack ensures that the connectors can reach the computer and the hub comfortably. 6. Starting at one end of each cable run, secure the cable to the walls, floor, or woodwork, and work your way to the other end. a. Make sure that (1) None of the cables are compressed or kinked anywhere along their length (2) All cables are protected from damage caused by foot traffic or furniture 7. When the cables are secured, plug one end of each cable run into the hub and the other end into the computer or other device. a. When the hub is connected to a power source and the computer is turned on, you should see the following indications of a proper connection: (1) The link pulse lights in the hub (2) The computer’s network interface adapter (if any) lights up. F. The network that is best suited for an external cable installation is one in which all of the computers and other devices are located in the same room. |4| 1. For a one-room network, run the cables around the room next to the walls, securing them to the baseboard or running them behind furniture. 2. You can purchase prefabricated UTP cables in a variety of colors to match your décor and keep the installation as discreet as possible. 3. Avoid running loose cables across a floor. a. Loose cables are a hazard to foot traffic. b. Stepping on cables can eventually damage them. 4. Running cables to computers or other devices in the center of a room can be a problem. Following are some workarounds to this problem: |5| a. Use rubber cable protectors that run across the floor. b. Run prefabricated cables through a drop ceiling and down through a ceiling tile to the appropriate location on the floor. c. Use thin floor-to-ceiling service poles to provide a safe cable conduit and a neater appearance. d. If there are many cables running down through the ceiling, you should consider an internal installation instead. G. Securing external cables 1. It is possible to run cables around a room and leave them loose, but it is a better idea to secure them in place. 2 Outline, Chapter 15 Network+ Certification, Second Edition
a. Securing cables ensures that they will not move into a high-traffic area where they can be stepped on or otherwise damaged. b. Securing cables prevents people from accidentally yanking on the cable, which can damage the connectors and might cause injury. 2. Before securing cables, lay them out in the exact route from one connection to the other. a. Do not fasten the cables as you run them or you run the risk of falling short of the destination and having to start over. 3. Stapling cables a. Simplest and usually the least expensive solution b. Do not use the standard square staples used in most staple guns; they can crush the cable and damage the wires within it. c. You can use individual staples or a cable holder. (1) Individual staples have a cap at the top that simplifies the task of hammering it into the wall. (2) A cable holder consists of a semicircular plastic sleeve with a wire brad through it. (3) Hammering the brad into the wall anchors the sleeve with the open end into the wall. d. You can also use a staple gun designed specifically for cable installations that shoots round-headed staples and has an adjustable depth setting. e. Staples should be secured well but should also allow the cable to be pulled through them freely. (1) If the cable cannot move laterally through the staple, the staple is too tight. f. If you accidentally pierce the cable sheath with a staple, start over with a new cable. |9,10| 4. Cable ties a. Loops of plastic or fabric that secure to a surface and can hold one or more cables (1) Some cable ties use a nylon hook-and-ratchet design (much like the flexible handcuffs that police use) and come with an eyelet for nailing the tie to a wall. (2) Some cable ties consist of a wider loop of cloth or plastic, the ends of which are attached using a hook and loop fastener, such as Velcro. b. Cable ties are more visible than staples and are more often used to secure bundles of cables in place. 5. Staples and cable ties are excellent solutions for securing cables to a wall or other surface, but they do not provide protection from objects that might bump into the wall and squeeze the cable. a. If possible, secure the cables so that they do not contact furniture or other objects. |11,12| 6. Raceways Outline, Chapter 15 3 Network+ Certification, Second Edition
a. A raceway is a small, enclosed conduit, usually made of plastic, that holds cables inside and is designed to run along walls. b. Advantage: provides better protection than staples or cable ties c. Disadvantage: more expensive and more difficult to install than staples or cable ties d. Some raceways screw to the wall and others have an adhesive backing. e. Because the raceway completely encloses the cables within a rigid housing, the cables are protected from bumps and abrasions. f. Because raceways are rigid, you must purchase fittings of exactly the right size and shape. g. Raceway products are usually modular. (1) You can buy straight runs, corners, and other components separately, all of which fit together. h. You can also get surface-mounted connection boxes that attach to the raceway, so you can run bulk cable and connect it directly to the jacks in the boxes. (1) Using these connecton boxes is the functional equivalent of performing an internal installation without having to run cables inside walls or ceilings. |13| H. Running cables around doors 1. Doorways are one of the most common obstacles encountered during a one-room external cable installation. a. If you can avoid doorways by running your cables the long way around the room, you should do so. 2. Running cables on the floor across a doorway’s threshold a. Avoid whenever possible b. Exposes the cable to repeated compressions from foot traffic that can eventually damage the wires inside c. Running the cable underneath the threshold is preferable if there are no exposed sharp edges that might cut the cable sheath. 3. Running cables up and around a doorway a. Use staples to hold the cable in place. b. Use cables that are close to the color of the walls, or paint over the cable after it is installed. c. Disadvantages: (1) Can be unsightly because it brings the cables up to eye level (2) Adds significantly to the length of cable d. Running multiple cables over a single doorway can be even more problematic. (1) Consider adding another hub to your network so that you can get by with only one cable over the doorway. (2) Consider using a raceway large enough to hold multiple cables. I. Running cables to other rooms 4 Outline, Chapter 15 Network+ Certification, Second Edition
1. External installations are complicated when you have computers in different rooms. 2. To run cable to a different room, you can go through the door or through the wall. a. To run cable through a doorway, there must be sufficient space between the bottom of the door and the floor for the cable to pass through, even when the door is closed. b. To run cable through a wall (1) Select a spot on the wall that is covered by furniture in both rooms (2) Drill a hole from one room to the other that is large enough to pass the cable (and connector) through c. Taping one end of the cable to a length of straightened wire makes it easier to thread the cable through the wall to the other side. 3. Safety considerations a. When drilling through walls, be sure to avoid any cables or pipes that might be inside the wall. b. Although it might be tempting to use a very long drill bit to go through both sides of the wall at once, it is usually safer to drill a hole in one side, use a long screwdriver to probe around inside the wall, and then poke a hole through the far wall on the other side. (1) Using this method, you will not accidentally drill through a vital service connection. (2) This method also ensures that the holes in both sides of the wall align properly. |14| J. Running cables between floors 1. The most difficult type of external installation is one that spans two or more floors of the same building because a. It can be difficult to find an appropriate place to run the cables b. The installation might require special tools 2. In a wooden structure, you must carefully plan the location of the hole from both above and below, so that you do not end up with a cable hanging down through the middle of a ceiling. a. If both floors have walls in the same places, you can sometimes drill through the floor inside a wall, using your wall plate holes for access to the interior of the wall. b. One method of finding the proper location for the hole: (1) Drill a 1/8-inch-diameter hole down through the floor right next to the wall. (2) Push a bent coat hanger through the hole to mark the location. (3) From the floor below, find the protruding coat hanger, measure about 2 inches from the first hole in the direction of the wall, and drill a 3/4-inch hole upward. (4) Push the cable up through the floor and grab the cable from above. Outline, Chapter 15 5 Network+ Certification, Second Edition
(5) Make sure that you do not disturb any of the building’s service connections in the process. 3. In an office building, you are more likely to find a conduit between floors that you can use to run your cables. a. If the conduit is also an air space that is part of the building’s ventilation system, use the proper cable for the installation. (1) Failure to use the correct cable can result in penalties and can force you to reinstall the cable. 4. If no conduit exists, you might have a difficult time because the floors in commercial office buildings are often made of concrete that is several inches thick. a. Drilling through a concrete floor might require heavy tools and a consultation with an engineer and building inspector. 2. Internal Installations A. Most professional cable installations are internal. 1. All of the cables are run inside walls, ceilings, or floors. |15| B. Internal cable installations split the connection into three parts: 1. The main part of the connection is a length of bulk cable that runs from a wall plate at the computer’s location to a patch panel at the location of the hub. 2. The other two elements are relatively short, prefabricated cables called patch cables, which connect the computer to the wall plate and the patch panel jack to a hub port. |16| C. Internal installations use bulk cable, which is a long, unbroken length of cable, usually supplied on a large spool, with no connectors attached. 1. The installer pulls off the length of cable needed for a run, cuts it off the spool, and attaches the ends to the wall plate jacks and the patch panel jacks. 2. Prefabricated, or patch, cables are relatively short and already have RJ-45 connectors attached. 3. You can also buy modular RJ-45 connectors and attach them to lengths of bulk cable yourself to make your own patch cables. 4. To use bulk cable, you must have the appropriate tools and fittings to attach connectors to both ends. 5. Advantages of bulk cabling: a. It is easier to pull the cable without the connectors attached to it. b. You have greater flexibility in the types of connectors you use. c. You save money by buying cable in large quantities. 6. Cable intended for use as a patch cable or an external cable is generally made from stranded wire. a. Stranded wire allows the cable to be more flexible but makes it difficult to use for internal cable installations, which rely on punchdown connections. b. Cable for internal installations generally uses solid wire conductors, which work well with the punchdown connectors. 6 Outline, Chapter 15 Network+ Certification, Second Edition
c. Solid wire cable is a bit less expensive than stranded wire cable and is more resistant to attenuation. (1) Enables you to have longer cable runs d. For cable runs longer than 30 meters, you should always use a solid wire cable. D. Professionals who specialize in data and telephone cabling perform most internal cabling jobs. 1. In new construction, both data and telephone cable systems are often installed simultaneously. 2. Pulling cable for this type of installation is not especially difficult, but it helps to have the proper tools and a strong sense of organization. 3. When installing a large network, it is important to proceed systematically and label each cable run carefully. |17| E. Internal cable installation procedure 1. Select the locations for your computers and other network-connected devices and a central, protected location for your hubs and patch panel. a. One end of all your cable runs will terminate at the patch panel. (1) Be sure to select a location with sufficient access to the entire site, away from possible sources of electromagnetic interference, and with room to work easily. 2. Plan the routes for your cables from the patch panel to the location of each wall plate or other connector. a. Take into account all obstacles, such as barrier walls, light fixtures, and plenums. 3. With your spool of bulk cable located at the patch panel site, label the lead end of the cable with its intended location. 4. Feed the lead end of the bulk cable into the ceiling, wall, or floor that you will install it in, and then pull the cable to the location of the wall plate. a. Do not cut the cable off the spool until you have pulled it all the way to the wall plate. b. Leave several yards of slack inside the ceiling, wall, or floor to avoid problems making the connections or locating the equipment. 5. Secure the cables along their routes so that they cannot shift location or be damaged by other people working in the same area. 6. Label the end of the cable with the name of the wall plate location and cut the cable from the spool. a. Never cut an unlabeled cable from the spool. 7. Begin the cable connection procedure. F. The difficulty of an internal cabling job depends on the construction of the site. 1. The typical office building, with plasterboard walls and drop ceilings, is an ideal environment for cable installation. a. You can usually run the cables freely through the ceiling to any room on the floor, and then drop them down inside the walls to a wall plate at almost any location. Outline, Chapter 15 7 Network+ Certification, Second Edition
|18| 2. You might encounter a variety of obstacles: a. Sources of electromagnetic interference that can disturb data signals b. Fire breaks that prevent you from running cable down from the ceiling c. Asbestos insulation d. Service components, such as ventilation ducts and light fixtures e. Structural components, such as concrete pilings and steel girders 3. All of these obstacles should have been detected during the planning stage, however, and you should have established a proper route around or through them for each cable run. |19| 4. Safety considerations and legal implications a. You should never cut, drill through, or otherwise disturb a structural member of a building without consulting someone with full knowledge of the consequences. b. Apart from engineering concerns, there are local fire laws and building codes to consider. (1) Violating fire laws and building codes means that you, the installer, might be held responsible, not only for making the job right later, but for any applicable fines and penalties. (2) If you outsource the cabling job to a contractor, your contract should stipulate that the installer is responsible for the legality of the installation. 5. In some buildings, you might run into conditions that make an internal cable installation difficult, if not impossible. a. If there is no access to the interiors of ceilings or walls, consider other solutions, such as an under-floor cable installation or surface- mounted raceways. G. Installing a cable run 1. When installing multiple cable runs, you typically start at the location of the patch panel, which is where one end of all the cable runs will terminate. 2. With your spool of bulk cable at the patch panel location, you typically proceed by a. Stripping a few yards of cable off the spool b. Threading it through the ceiling to the proper location c. Leaving extra cable to reach the locations of the connectors, and only then cutting it off the spool 3. Be sure to label each end with a piece of tape or some other type of tag so that you can tell which cable is which. 4. It is essential that you have a master diagram of the space with all of the cable runs and their names. a. This is important not only for installation, but also for troubleshooting afterward. 5. The process of pulling the cable through the ceiling space is the actual work of installing cable. 8 Outline, Chapter 15 Network+ Certification, Second Edition
a. The process goes much more smoothly when at least two people work together, so that one person can pass the cable inside the drop ceiling to the other person. |20,21,22| 6. Tools often involved in the cable installation process a. Ladders b. A ball of string (1) If you have multiple cable runs going to destinations that are close together, you can tape one end of a length of string to the leading end of your cable. (2) After you get the cable to its destination, you can tape the other end of the string to another cable and pull it through the ceiling to the same destination. c. Prefabricated cable pullers d. A telepole, which is a telescoping pole, rather like a collapsible fishing rod, with a hook at one end to which you connect a cable. (1) You carry the collapsed telepole with the attached cable into the ceiling, then extend the pole and hand off the cable end to the next person down the line. e. Yardsticks or flexible nylon rods to push through the ceiling f. A tennis ball with one end of a length of string taped to it (1) Throw the ball through the ceiling and use the string to pull a cable through along the same route. g. The “coil and throw” technique, where a person on one ladder coils up a length of cable and throws it to a person on another ladder some distance away H. Securing cables 1. It is just as important to secure internally installed cables as it is to secure external ones, to prevent them from being moved. a. Maintenance people have access to light fixtures, ventilation ducts, or other components, and securing your cables ensures that they do not get moved closer to possible sources of damage or interference. 2. An advantage of a drop ceiling is that the framework used to suspend the ceiling panels provides many places to secure cables. 3. Nylon cable ties are good for securing cables, as are the plastic ties that sometimes come with trash bags. I. Dropping cables 1. After you have pulled the cable to the approximate location of the computer or other device it will connect to, drop it down inside the wall where you want to affix the wall plate. 2. Most commercial office buildings use metal studs and do not have horizontal cross members inside the walls, which makes it relatively easy to drop cables to wall plate locations down near the floor. |23| 3. To drop a cable vertically, inside a wall: a. Cut a hole in the wall where you will install the wall plate. b. Thread the cable down inside the wall from the ceiling. c. Pull the cable out through the hole. Outline, Chapter 15 9 Network+ Certification, Second Edition
d. Later, attach the cable to the connector in the wall plate, push the excess cable back into the wall, and plug the hole by mounting the wall plate over it. 4. If a horizontal barrier inside a wall prevents the cable from dropping down to the location of the wall plate, you have several options: a. Cut another hole in the wall to drill through the barrier. (1) This is more feasible if the barrier is wood and not metal, but in any case, you will have to patch the wall afterward. b. Move the wall plate to the left or right and try to find a passage in the wall that is not blocked. c. Install a raceway from the ceiling down to a surface-mounted connection box. |24| 5. You can use a fish tape, which consists of a flexible band of metal or fiberglass that winds up on a reel and has a hook on the end, much like a plumber’s snake. a. You push the tape up to the ceiling through the hole in the wall, attach the cable to the hook, and pull it down and out through the hole. b. You can also run the tape down and out through the hole to pull a cable up to the ceiling, or through the ceiling to the floor above. 6. Depending on where and how you will install your patch panel, you might also have to drop the other end of your cable runs down through a wall. a. Smaller networks often use patch panels that mount on a wall, and you can drop the cables down to a hole that will eventually be located behind the mounted panel. b. Larger networks might use rack-mounted equipment, and the cables can drop down from an open ceiling into the back of the rack assembly. |25| J. Pulling other cable types 1. UTP cable is easy to install because it is thin and quite flexible. 2. Other types of cable have different properties, however, that can make the process of pulling cable more difficult. 3. The RG-58 coaxial cable used for thin Ethernet networks is roughly the same diameter as UTP, but it is heavier and much less flexible. 4. It is possible to install RG-58 coaxial cable internally, but it does not bend around corners as tightly as UTP cable does. 5. The biggest problem with an internal coaxial installation is the fact that thin Ethernet networks use a bus topology. a. You must pull one length of cable to each computer and then pull another length of cable from that computer to the next one. b. Two cables must protrude from the wall to a T-connector mounted on the computer’s network interface adapter to connect it to the network properly. 6. Thick Ethernet networks use RG-8 coaxial cable, which is nearly half an inch thick and very inflexible. 10 Outline, Chapter 15 Network+ Certification, Second Edition
a. This type of cable is hardly ever used today, but even in its heyday it was rarely installed internally b. The main advantage of thick Ethernet is that each computer uses a separate cable that connects the network interface card (network interface adapter) to the main RG-8 trunk, so only one cable protrudes through the wall. 7. Pulling fiber optic cable is roughly similar to pulling UTP cable. a. The multimode fiber used for most local area network (LAN) connections is reasonably flexible. (1) Because of the nature of the medium, the cable must be placed more precisely with respect to the bend radius as it turns around corners. b. One advantage of fiber optic cable is that it is immune to electromagnetic interference. (1) Many of the obstacles that you must normally route copper- based cables around, such as fluorescent light fixtures, do not affect a fiber optic installation. K. Pull all of your cable runs before you begin making connections to wall plates and patch panels. 1. You can then move cables as needed and bundle them together before they are permanently affixed. 2. Label all your cables at both ends so that when you make your connections, you know which cable you are holding. 3. After all the cables are pulled, you can begin making the connections. Chapter 15, Lesson 2 Making Connections 1. Two-Computer Networking |26| A. The simplest LAN consists of two computers, with network interface adapters installed, connected by a single cable. 1. When Ethernet networks used coaxial cable, it was possible to connect the network interface adapters in two computers with a thin Ethernet cable to set up a simple network. 2. Today’s Ethernet networks use UTP cable, which generally requires a hub. B. Ethernet hubs provide a vital service by crossing over the signals between the transmit and receive wires. 1. The signals sent over the transmit wires by each computer arrive at the receive connections at the other computers. 2. When you connect two Ethernet network interface adapters directly using a UTP cable, there is no hub, and this crossover is absent. 3. On a UTP Ethernet network without a hub, the two computers can be no more than 100 meters apart. Outline, Chapter 15 11 Network+ Certification, Second Edition
a. The hub on a standard UTP network functions as a repeater, enabling each cable connecting a computer to the hub to be 100 meters long, for a total span of 200 meters. C. To enable two directly-connected Ethernet computers to communicate, you must use a crossover cable. 1. A crossover cable wires the transmit contacts in each connector to the receive contacts in the other connector. 2. If you are connecting two computers in the same room, you can buy a prefabricated crossover cable and plug the ends into the network interface adapters in the two computers. 3. Crossover cables are not as commonly found in the average computer store as standard cables, hubs, and network interface adapters. a. You can order one from a catalog or Web retailer. 4. To connect two computers in different rooms or on different floors, using a crossover cable, you might have to perform an internal installation. a. In this case, you use the same cable and the same installation procedure for a crossover connection as you use for a hub-based network. b. The difference between a crossover installation and a standard installation is in the attachment of the wires to the connectors at each end of the cable. D. A UTP cable contains eight separate wires, which are joined together in four twisted pairs. 1. The RJ-45 connector at each end of the cable has eight conductive contacts that the eight wires are attached to. 2. When you plug a male connector into a female one, the corresponding contacts touch, creating electrical circuits. |27| 3. Functions of the eight contacts on a standard 10Base-T or 100Base-TX Ethernet network: a. 10Base-T and 100Base-TX networks use only four of the eight wires in a UTP cable, but 100Base-T4 networks use all eight. b. The four wires that are designated as unused can carry signals in either direction on a 100Base-T4 network. |28| E. Standard network cable runs and prefabricated cables use straight- through connections. 1. In a straight-through connection, each wire is attached to the same contact in both connectors. 2. The transmit contacts at one end are connected to the transmit contacts at the other end, and the receive contacts are connected in the same way. a. This is possible because the crossover circuit is supplied in the hub, which makes installation much easier. |29| F. To create a crossover connection in the cable, you must connect the two transmit contacts to their corresponding receive contacts. 1. The positive transmit data (TD+) contact at each end is connected to the positive receive data (RD+) contact at the other end. 12 Outline, Chapter 15 Network+ Certification, Second Edition
2. The two negative transmit data (TD–) contacts are connected to the two negative receive data (RD–) contacts. 3. When you install a cable using a crossover connection, you cannot use the cable run with a hub, because the crossover circuit in the hub would cancel out the crossover circuit in the cable. a. The TD+ contact that is crossed to the RD+ contact in the cable would be crossed again, back to the TD+ contact, inside the hub. b. The only way to use a crossover cable with a hub is to plug the cable into the hub’s uplink port, which does not run through a crossover circuit. 2. Connecting External Cables |30| A. For an external network, making your final connections is simply a matter of plugging them in to the hub and the computers. 1. Set up the hub in a central location, preferably where it is protected from traffic or vibrations that can pull on or loosen the cable connections, and connect it to a power source. 2. Plug the connector for each cable into one of the hub’s ports, and then push it firmly into the socket until it clicks. a. Do not use the hub’s uplink port for a computer connection unless the port has a switch that allows the crossover circuit to be disabled. b. Most hubs have light-emitting diodes (LEDs) that correspond to the ports. (1) The LEDs will not be lit until you connect the other end of the cables to the computers and turn them on. 3. At the other end of each cable, you should have a computer that is set up and ready to go. 4. Shut down the computer and plug the network cable into the jack provided by the computer’s network interface adapter, making sure that it clicks into place. a. If the jack does not fit in the socket, you are probably trying to plug the cable into a modem jack, which will not work. b. Most Ethernet network interface adapters have an LED next to the RJ-45 connector. (1) The LED lights up when the network interface adapter is connected to an operating hub. B. Link pulses 1. When you turn on the computer, the network interface adapter generates a signal called a link pulse and transmits it over the cable. 2. When the hub receives the signal, it responds with a signal of its own. 3. If either the network interface adapter or the hub is a Fast Ethernet device, the devices use these link pulse signals to negotiate the fastest speed they have in common. a. For example, when you plug a dual-speed network interface adapter into a Fast Ethernet hub (1) The link pulse signals enable the two devices to determine that they are both capable of operating at 100 Mbps Outline, Chapter 15 13 Network+ Certification, Second Edition
(2) The two devices configure themselves to use that speed 4. If you connect a dual-speed network interface adapter to a standard Ethernet hub, the network interface adapter determines that it must run at 10 Mbps to use the hub, and it adjusts itself accordingly. 5. When this negotiation is complete, the LEDs on both the hub and the network interface adapter should light up. a. Some dual-speed network interface adapters have two LEDs, one of which specifies the speed the card is operating at. b. If the LEDs do not light up, there might be a problem with your cable connection, or possibly with the network interface adapter or hub. 3. Connecting Internal Cables |31| A. Final connections procedure for an internal cable installation 1. Connect one end of the cable run to a port in a patch panel. 2. Connect the patch panel port to a hub port using a patch cable. 3. Connect the other end of the cable run to a port in a wall plate. 4. Mount the wall plate in the wall. 5. Use a patch cable to connect the port in the wall plate to the network interface adapter in a computer. B. Connector components 1. When you install bulk cable, you must purchase the connectors you need and the tools for attaching the connectors separately. 2. Wall plates a. Most internal installations use wall plates for the computer end of each cable run and one or more patch panels for the hub end. (1) A wall plate is a metal or plastic face plate that screws into a hole in a wall, much like an electrical outlet, except that the wall plate contains female RJ-45 connectors (jacks). b. A connector on the back of the wall plate jack contains the contacts that you attach the wires to inside the UTP cable. c. Some wall plates have integrated jacks, while others are modular. d. You can buy wall plates that hold one, two, four, or more jacks, and you can insert different types of jacks to support various cable connections. e. When the cable is connected and the wall plate is installed, the cable is hidden in the wall, and the only part visible is the front of the wall plate. (1) You can then plug a patch cable into the jack, just as you would a telephone cable. f. Although it is perfectly acceptable to use one wall plate for both telephone and data network connections, these two services must use separate cables. (1) It is not safe to use the two unused wire pairs in the typical UTP Ethernet network for voice traffic because voice signals can cause crosstalk that interferes with the data signals on the other wires. 14 Outline, Chapter 15 Network+ Certification, Second Edition
|32| 3. Patch panels a. A patch panel is similar in function to a wall plate, except that it supports many more ports. (1) Sometimes called a punchdown block b. A patch panel is essentially a face plate or box with a number of RJ- 45 jacks mounted in it. c. A patch panel is not a hub; it is nothing more than a nexus that is a convenient place to terminate the hub end of all your cable runs. d. You plug patch cables into the patch panel’s ports to connect them to hub ports, thus completing the connection at that end. e. Patch panels are available in a variety of sizes and configurations, and are either mounted on a wall or integrated into a rack-mounted system. f. Make sure that all the jacks you use on your network conform to the same rating as your cables. (1) If you are installing Category 5 cable, you must use jacks that are rated for Category 5 as well. C. Punching down 1. The process of connecting the ends of your bulk cable runs to the jacks in your wall plates and patch panels is called “punching down.” |33| 2. Punching down a cable consists of the following steps: a. Strip some of the insulating sheath off the cable end to expose the wires. b. Separate the twisted-wire pairs at the ends. c. Strip a small amount of insulation off each wire. d. Insert the wires into the appropriate contacts in the jack. e. Press the bare wire down between the two metal contacts that hold it in place. f. Cut off the excess wire that protrudes past the contacts. g. Repeat this process at both ends for each internal cable run. |34| 3. Punchdown block tools a. A punchdown block tool is a handheld device that you use to insert each wire between its set of contacts. b. The tool strips the insulation off the wire, presses it into place between the contacts, and cuts off the excess wire. c. An essential tool for an internal UTP cable installation (1) Without the punchdown tool, the process of stripping, installing, and cutting each wire is very laborious. d. The punchdown block tool must be the same type as your jacks. (1) The types usually refer to the configuration of the blade that cuts off the wire ends. (2) The jacks (or blocks) most often used today are called 110-style. 4. The most important part of the punchdown process is matching the wires with the correct contacts. Outline, Chapter 15 15 Network+ Certification, Second Edition
a. The wires inside the UTP cable are color-coded orange, green, blue, and brown. b. The positive wire in each pair is solid-colored, and the negative wire has a white stripe. c. You can buy jacks that have corresponding colors on the contacts, so that you simply have to match up the wires with the same-colored contacts when punching down. |35| 5. Wiring standards a. Two standards, called 568A and 568B, specify which color wire in a UTP connection should be associated with each contact on the connector. (1) These standards are found in two versions of the Electronics Industry Association/Telecommunications Industry Association (EIA/TIA) 568 "Commercial Building Telecommunication Cabling Standard" document. b. The standard you choose when wiring your connectors is not important, as long as you select a wiring configuration and use it consistently throughout the entire cabling project. c. A cable wired per the 568A standard on one end and the 568B standard on the other will not function. d. If several people are working together to install the cable, make sure that they all use the same wiring standard. 6. Using a punchdown block tool a. Begin by stripping about 2 inches of sheathing off the end, and then untwist each of the four wire pairs. |36| b. Lay down the cable in the center of the jack and spread out the wires so that they lay out between the appropriate sets of contacts. (1) The beginning of the cable sheath should be no more than one- eighth of an inch from the jack c. Untwist each wire pair only as much as necessary for the wire to fit between the contacts. (1) The twists provide an essential function by preventing the signals on the various wire pairs from interfering with each other. (2) Each pair uses a different number of twists per foot, and you want to preserve this configuration as much as possible. d. Take the punchdown tool and place it over the first set of contacts, with the blade on the outside of the jack and the handle of the tool tilted slightly outward. (1) Press down firmly on the tool. (2) This presses the wire into place, stripping off the insulation as it goes, and cutting off the loose wire end. e. Repeat this process for the remaining seven wires, and be sure to remove the wire ends that are cut off. f. After you have punched down all eight wires, do the following: (1) Insert the jack into the wall plate or patch panel (if necessary). 16 Outline, Chapter 15 Network+ Certification, Second Edition
(2) Mount the wall plate into the hole you cut previously, pushing all of the excess cable inside the wall. (3) Mount the patch panel on the wall or rack after you have punched down all of the cables. D. Installing patch cables 1. A patch cable is a shorter length of cable with standard male RJ-45 connectors on both ends, which you can use to connect a. A wall plate to a computer’s network interface adapter b. A patch panel port to a hub port 2. Making the final connections is no different from the process for an external cable installation. E. Attaching connectors 1. Although wall plates and patch panels make for a neater installation, you can also attach male RJ-45 connectors to the ends of your cables and plug them directly into your hubs and computers, just as you would with prefabricated cables. a. You can also attach these connectors to shorter lengths of cable, to build your own patch cables. 2. Male RJ-45 connectors for UTP come in three configurations; ensure that your RJ-45 connectors are compatible with the selected cable, as follows: a. Round cable with stranded wire b. Round cable with solid wire c. Flat cable (commonly referred to as “silver satin”) with stranded wire (1) Silver satin cables are designed for telephone network connections and should not be used for data networking. |37| 3. Attaching male RJ-45 connectors to UTP cable requires another special tool, called a crimper. a. A jawed device that looks like a pair of pliers, with a set of dies that let you squeeze the two halves of an RJ-45 connector together with the wires inside b. The crimping procedure is similar to the punchdown procedure. (1) Strip some of the sheath off a cable and lay the wires out in the bottom half of the connector, making sure you use the same wiring standard at both ends. (2) Lay the other half of the connector on top of the wires and squeeze the handles of the crimper to lock the two halves together. c. Prefabricated patch cables might be a more economical alternative. (1) Consider the price of the crimper and the dies (about $50), the bulk cable and the connectors you will ruin while learning how to crimp, and the value of your time. F. Making fiber optic connections 1. The fiber optic cable attachment procedure is different from the copper cable attachment procedure. Outline, Chapter 15 17 Network+ Certification, Second Edition
2. The connectors used on fiber optic cables, called straight tip (ST) and subscriber connectors (SC), are just sleeves that fit around the end of the cable and let the central core protrude out the end. 3. The only function of the connector is to lock the signal-carrying core in place when it is plugged into the jack |38| 4. The process of attaching a connector to a multimode fiber optic cable consists of the following basic steps: a. Strip off the outer sheath from the end of the cable. b. Glue the connector in place, using an epoxy adhesive. c. Allow the adhesive to cure. d. Polish the protruding core so that the pulses of light carried by the cable reach their terminus in the best possible condition. 5. Singlemode cables are terminated by permanently splicing a “pigtail” to them. a. A pigtail is a short length of cable with a connector already attached to it. b. Splicing a pigtail is necessary because the tolerances for singlemode fiber are much tighter than those of multimode. |39| Chapter Summary A. Pulling cable 1. External unshielded twisted-pair (UTP) cable installations use prefabricated cables to connect computers directly to hubs. 2. Internal cable installations use bulk cable, which you pull through walls, ceilings, or floors. B. Making connections 1. To connect two computers without a hub, you must use a crossover cable connection, which reverses the transmit and receive signals. 2. External cables have the connectors attached, and you simply plug them into your computers and hubs to make the final connections. 3. For internal cables, you must manually attach a jack at each end, which becomes part of the wall plate or patch panel. 4. The process of attaching a jack is called punching down; it requires a specialized punchdown block tool. 18 Outline, Chapter 15 Network+ Certification, Second Edition