Installing network cables is often called "pulling cable," because the process can involve threading one end of a cable through a wall or ceiling and then pulling the rest of the cable through from the other end. Depending on the type of cable involved and the nature of the site, installing cable can be very simple or extraordinarily complex. This lesson concentrates primarily on the installation of unshielded twisted pair (UTP) cable, which is by far the most popular network medium used today.
An external installation is one in which you use prefabricated UTP cables and run them from each computer to the hub in the room where the equipment islocated. You don't have to run cables through walls or ceilings, attach connectors to bulk cable, or purchase additional hardware, such as wall plates and patch panels. External installations are also portable; you can coil up the cables and take them with you if you have to move the network. The drawbacks of an external installation are that the cables are often left visible, and obstacles between the various pieces of network equipment can make running the cable difficult. However, there are steps you can take that help to minimize these drawbacks.
The fundamental parts of an external cable installation are as follows (moredetailed information about the individual steps of the procedure is provided later in this lesson):
The network that is most obviously suitable for an external cable installation is one in which all of the computers and other devices are located in the same room. A one-room network eliminates the single biggest problem of external cable installations: running cables between rooms, or worse, between floors. For a small, one-room network, you can generally run the cables around the room next to the walls, securing them to the baseboard or running them behind furniture, as shown in Figure 15.1. You can purchase prefabricated UTP cables in a variety of colors to match your décor and keep the installation as discreet as possible.
Figure 15.1 A simple external installation runs cables around the perimeter of the room
One thing you want to avoid in any cable installation is a loose cable running across a floor. Not only is this a hazard to foot traffic, but stepping on cables can eventually damage them, causing intermittent network outages that are difficult to troubleshoot.
Problems arise if you have to run cables to computers or other devices that are located in the center of the room and not next to a wall. There are several solutions to this, depending on your environment. You can buy rubber cable protectors that run across the floor; a cross-section of two cable protectors is shown in Figure 15.2. These provide a safe conduit for the cable and prevent people from tripping over it. You can also run prefabricated cables through a drop ceiling and down through a ceiling tile to the appropriate location on the floor. This can look odd, although it is possible to purchase thin floor-to-ceiling service poles that provide a safe cable conduit and a neater appearance. When you begin thinking about running cables through the ceiling, however, you should consider whether an internal installation might be a better idea.
Figure 15.2 Rubber cable protectors might be unsightly, but in situations where you must run cables across the floor, they provide effective protection
Although it's possible to run your cables around a room and leave them loose, it's a good idea to secure them in place. Securing the cables ensures that they won't move into a high-traffic area where they can be trodden on or otherwise damaged. It also prevents people from accidentally yanking on the cable, which can damage the connectors. There are a number of hardware solutions you can use to secure your cables in place. However, you should first lay out your cables in the exact route from one connection to the other. Don't fasten the cables as you run them or you run the risk of falling short of the destination and having to start over.
Stapling cables to walls or baseboards is the simplest—and usually the least expensive—solution. However, do not use the standard square staples used in most staple guns because they can crush the cable and damage the wires within it. Instead, buy individual staples. An individual staple either has a cap at the top that simplifies the task of hammering it into the wall, or it has a cable holder that consists of a semicircular plastic sleeve with a wire brad through it. Hammering the brad into the wall anchors the sleeve with the open end into the wall, as shown in Figure 15.3.
Figure 15.3 Individual staples hold cables securely to a surface without squeezing the sheath
If you have a significant amount of cable to install, it might be worth the expense to buy a staple gun designed specifically for cable installations, like the one shown in Figure 15.4. This type of staple gun shoots round-headed staples and has an adjustable depth setting. The idea is for the staples to be well secured in the wall while the cable can be pulled through them freely. If the cable cannot move laterally through the staple, the staple is secured too tightly. If you accidentally pierce the cable sheath with a staple, you should start over with a new cable. This type of stapler might not be available at your local home center, but computer dealers that carry bulk cable and other network cabling supplies often have them. A good stapler of this type can use square as well as round-topped staples, so it's not completely useless for doing other jobs.
Figure 15.4 A cable stapler shoots round-headed staples and has an adjustable depth setting
Another option for securing cables in place is to use cable ties, which are loops of plastic or fabric that secure to a surface and can hold one or more cables. Some of these products use a nylon hook-and-ratchet design (much like the flexible handcuffs that police use) and often come with an eyelet for nailing the tie to a wall. Others consist of a wider loop of cloth or plastic, the ends of which are attached using a hook and loop fastener, such as Velcro. An example of a cable tie is shown in Figure 15.5. Such ties are more visible than staples and they are more often used to secure bundles of cables in place. An advantage of the Velcro ties is that they can be opened so you can add more cables as your network grows.
Figure 15.5 A cable tie
Both staples and cable ties are excellent solutions for securing cables to a wall or other surface, but they don't provide any protection from objects that might bump into the wall and squeeze the cable. If at all possible, you shouldsecure the cables in such a way as to make it difficult for furniture or otherobjects to come into contact with the cables.
Another option for securing cables that also provides better protection than staples or cable ties is called a raceway. A raceway is a small, enclosed conduit, usually made of plastic, that holds cables inside and is designed to run along walls. Some raceways screw to the wall and others have an adhesive backing; the screw-in models are definitely more secure. Because the raceway completelyencloses the cables within a rigid housing, they are protected from bumps and abrasions.
Raceways are more expensive and more difficult to install than staples or cable ties. Because raceways are rigid, you have to purchase fittings of exactly the right size and shape, but they allow you to run the cables up and down walls or around corners or doorways while completely enclosing them. The products are usually modular, meaning that you can buy straight runs, corners, and other components separately, all of which fit together, as shown in Figure 15.6. Raceway products usually come in a limited range of colors; most are a neutral putty color, which, depending on your décor, may or may not be very noticeable.
Figure 15.6 Raceways completely enclose cables and protect them from damage
In some cases, you can also get surface-mounted connection boxes thatattach to the raceway, enabling you to run bulk cable and connect it directly to the jacks in the boxes. This is the functional equivalent of an internal installation without having to run cables inside walls or ceilings. If you are installing a network in a building with cinderblock walls, for example, this could be your only option for a bulk cable installation.
One of the most common obstacles encountered during a one-room external cable installation is a doorway. Generally speaking, if you can avoid doorways by running your cables the long way around the room, you should do so, even if it means using a longer cable. However, sometimes you have no choice other than to run the cable past a doorway, and this leaves you two options. You can run the cable up and around the door or you can run it on the floor along the doorway's threshold.
In most cases, you should avoid the latter option. Even if you secure the cable to the floor very well, you expose it to repeated compressions from foot traffic that can eventually damage the wires inside. It is better to run the cable underneath the threshold, if possible. If there is a threshold in the doorway that you canremove temporarily, you can route the cable underneath it, as long as there are no sharp edges exposed that might cut the cable sheath.
Most of the time, however, you will have to run your cable up and over the doorway, using staples to hold it in place, as shown in Figure 15.7. This is usually not a difficult task, especially if there is a wooden molding around the doorway, but it can be unsightly because it brings the cables up to eye level. You might want to try to find cabling in a color that closely matches the walls, or even paint over the cable after it's installed.
Figure 15.7 Staple cables securely around a doorway rather than routing the cable on the floor across the doorway
Running multiple cables over a single doorway can be even more problematic. You might want to consider adding an additional hub to your network so that you can get by with only one cable over the doorway, or you might use a raceway large enough to hold multiple cables.
Running cable around a doorway adds significantly to its length, so be sure to factor doorways into your cable length estimations.
When you have computers in different rooms, even an external installation can become complicated. There are generally two ways to get a cable from one room to another: through the door or through the wall. Running cable on the floor across a doorway causes problems, but running cable through a doorway is often an acceptable solution. 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.
Running a cable through a wall is also an acceptable solution, even if it isn't strictly an external installation. The best course of action is to select a spot on the wall that's covered by furniture in both rooms and drill a hole from one room to the other that is large enough to pass the cable through. When you're running a prefabricated cable through a wall, drill holes that are large enough for the connector to pass through. 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.
When drilling through walls, be sure to avoid any cables or pipes that might be inside the wall. 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. Using this method, you won't accidentally drill through a vital service connection. This also ensures that the holes in both sides of the wall align properly.
In many cases, the most difficult type of external installation is one that has to span two or more floors of the same building. It can be difficult to find an appropriate place to run the cables, and the installation might require special tools. In a wooden structure, drilling a hole in the floor is relatively easy, but you must carefully plan the location of the hole from both above and below, so that you don't end up with a cable hanging down through the middle of a ceiling. 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. This might require a special drill with a right-angle chuck and a long bit, or you might be able to drill up through the floor from below. One method of finding the proper location for the hole is to drill a one-eighth-inch-diameter hole down through the floor right next to the wall and push a bent coat hanger through to mark the location. From the floor below, find the protruding coat hanger, measure about2 inches from your first hole in the direction of the wall, and drill a three-quarter-inch hole upward, as shown in Figure 15.8. You should then be able to push your cable up through the floor and grab it from above. As always, make sure that you don't disturb any of the building's service connections in the process.
Figure 15.8 Running cables up through a floor into the interior of a wall can be tricky, but it makes for a neater installation
In an office building, you are more likely to find some sort of conduit between floors that you can use to run your cables. In some cases, this conduit can also be an air space that is part of the building's ventilation system. If this is so, be sure you use the proper cable for the installation. Your local building codes mightrequire a plenum-rated cable, and failure to use the correct cable can result in penalties and a forced reinstallation. If no such conduit exists, however, you might have a difficult time because the floors in commercial office buildings areoften made of concrete that is several inches thick. Drilling through it might require heavy tools and a consultation with an engineer and building inspector.
For more information about plenum cables, see Lesson 1: Network Cables, in Chapter 2, "Network Hardware."
Most professional cable installations are internal, meaning that all of the cables are run inside walls, ceilings, or floors. Unlike an external installation, which typically uses a single prefabricated cable to run from each computer all the way to the hub, an internal cable installation splits the connection into three parts, as shown in Figure 15.9. The main part of the connection is a length of bulk cable that runs from a wall plate in the vicinity of each computer's location to a patch panel at the location of the hub. 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.
Figure 15.9 Each internal cable connection consists of three parts: a bulk cable connection inside the walls and two patch cables
This lesson deals with the process of pulling the cable from the location of the wall plate to the location of the patch panel. For more information about wall plates, patch panels, and connecting cables to them, see Lesson 2: Making Connections, later in this chapter.
Internal installations use bulk cable, which is a long, unbroken length of cable, usually supplied on a large spool, with no connectors attached, as shown inFigure 15.10. The installer pulls off as much as needed for a particular run, cuts it off the spool, and attaches the ends to the wall plate jacks and the patch panel jacks. Prefabricated, or patch, cables are relatively short in length and already have RJ-45 connectors attached. You can also purchase modular RJ-45 connectors and attach them to lengths of bulk cable yourself to make your own patch cables. This enables you to use only as much cable as you actually need, which is often considerably less than when you use prefabricated cables.
Figure 15.10 Bulk cable on spools
To use bulk cable, you must have the appropriate tools and fittings to attach connectors to both ends. The advantages of bulk cabling are that it is easier to pull the cable without the connectors attached to it, you have greater flexibility in the types of connectors you use, and you save money by purchasing cable in large quantities.
Cable intended for use as a patch cable or an external cable is generally made from stranded wire, which allows the cable to be more flexible, but makes itdifficult to use for internal cable installations, which rely on punchdown connections (described later). Cable for internal installations generally uses solid wire conductors, which work well with the punchdown connectors. Solid wire cable is a bit less expensive than stranded wire cable, and is more resistant to attenuation, enabling you to have longer cable runs.
Although Ethernet guidelines specify that you can have cable runs of up to 100 meters between a computer and a hub, you rarely, if ever, see a prefabricated cable that long. The stranded wire used in prefabricated cables is one of the reasons for this. For cable runs longer than 30 meters, you should always use a solid wire cable. It is also possible to purchase prefabricated solid wire cables from some specialty vendors.
Professionals who specialize in data and telephone cabling perform most internal cabling jobs. As mentioned earlier, in new construction, both data and telephone cable systems are often installed simultaneously. 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. When installing a large network, all those cables running through the same ceiling system tend to look alike, so it's important to proceed systematically and label each cable run carefully. That way you don't have to retrace your steps later.
The basic steps involved in installing internal cable runs are as follows:
To a large extent, how difficult an internal cabling job is depends on the construction of the site. The typical office building, with plasterboard walls and drop ceilings, is an ideal environment for cable installation. 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. Of course, these projects rarely come off without a hitch, and there are a variety of barriers that the cable installer might encounter. These barriers can include sources of electromagnetic interference that can disturb data signals, fire breaks that prevent you from running cable down from the ceiling, asbestos insulation, service components such as ventilation ducts and light fixtures, and structural components, such as concrete pilings and steel girders. All of these obstructions 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.
You should never cut, drill through, or otherwise disturb a structural member of a building without consulting someone with full knowledge of the consequences. Apart from engineering concerns, there are local fire laws and building codes to consider. Violating them means that you, the installer, might be held responsible, not only for making the job right later, but for any applicable fines and penalties. If you outsource the cabling job to a contractor, your contract should stipulate that the installer is responsible for the legality of the installation.
In other types of buildings, you might run into conditions that make an internal cable installation difficult, if not impossible. If there is no access to the interiors of ceilings or walls, consider other solutions, such as an under-floor cable installation or the surface-mounted raceways described earlier in this lesson.
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. The other ends can be spread out all over the floor, but one end of all these cables comes together at this one point. With your spool of bulk cable at the patch panel location, you typically proceed by stripping a few yards of cable off the spool, threading it through the ceiling to the proper location, leaving sufficient extra cable to reach the locations of the connectors, and only then cutting it off the spool. 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. It is essential that you have a master diagram of the space with all of the cable runs and their names. This is important not only for installation, but for troubleshooting afterward.
It's a good idea to leave some extra slack in your cable runs, which can be hidden inside a wall or ceiling, in case someone wants to move the location of the wall plate or patch panel later.
The process of pulling the cable through the ceiling space is the actual work of installing cable. The process goes much more smoothly when there are at least two people working together, so that one person can pass the cable inside the drop ceiling to the other person. The tools involved in this process are simple but essential. Several ladders are a must, of course, but beyond that you might be surprised to see what other tools professional installers use to pull cable.
A simple ball of string is often the cable installer's most valuable tool. 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. 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. There are also prefabricated cable pullers that you can buy, as shown in Figure 15.11, which might make the job a little bit easier.
Figure 15.11 A cable puller allows you to attach multiple cables and pull them all through a ceiling, wall, or floor at once
For moving the cable through the ceiling, you can stick to the basic "coil and throw" technique: A person on one ladder coils up a length of cable and throws it to a person on another ladder some distance away. Throwing the cable inside a small ceiling space can be difficult, however, and installers have come up with other methods, some of which are quite ingenious.
The "official" tool for extending cable through ceiling spaces is called a telepole. A telepole is a telescoping pole, rather like a collapsible fishing rod, with a hook at one end to which you connect a cable (see Figure 15.12). You carry the collapsed telepole with the attached cable into the ceiling; you then extend the pole and hand off the cable end to the next person down the line. This is a brilliant idea, but the telepole is a specialized piece of equipment that many installers find they don't really need. Many installers use yardsticks or flexible nylon rods that they push through the ceiling. With a little practice, even a tennis ball with one end of a length of string taped to it makes an effective cabling tool. Simply throw the ball through the ceiling and use the string to pull a cable through along the same route.
Figure 15.12 By connecting one end of a cable to the hook on a telepole, you can easily push it through wall or ceiling spaces
It's just as important to secure internally installed cables as it is to secure external ones. The object here is not so much cosmetic as it is to prevent the cables from being moved. Remember that you might not be the only person that goes poking around inside the drop ceiling. Maintenance people have access to light fixtures, ventilation ducts, or other components, and securing your cables ensures that they don't get moved closer to possible sources of damage or interference. Another advantage of a drop ceiling is that the framework used to suspend the ceiling panels provides many places to secure cables. Nylon cable ties are good for this purpose, as are the plastic ties that sometimes come with trash bags.
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. 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. In most cases, vertical cable drops are easily accomplished. Cut a hole in the wall where you will install the wall plate, thread the cable down inside the wall from the ceiling, and pull the cable out through the hole. Later, you 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.
If you encounter a horizontal barrier inside a wall that prevents the cable from dropping down to the location of the wall plate, you have several options. One option is to cut another hole in the wall to drill through the barrier. This is more feasible if the barrier is wood and not metal, but in any case, you will have to patch the wall afterward. Another option is to move the wall plate to the left or right and hope you find a passage in the wall that isn't blocked. As a last resort, you can entirely avoid dropping the cable inside the wall by installing a raceway from the ceiling down to a surface-mounted connection box. This is not as neat as a true internal cable run, but it's better than leaving a loose cable hanging from the ceiling.
As with horizontal cable runs, there are special tools that can make the process of dropping a cable easier. A fish tape is 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. 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. 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, as shown in Figure 15.13. Many professional installers havedevised their own tools for catching hold of cables inside walls. You can probably make do with a bent coat hanger most of the time.
Figure 15.13 You can use a fish tape to pull cables up and down inside walls
Depending on where and how you will be installing your patch panel, you might have to drop the other end of your cable runs down through a wall as well. 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. Larger networks might use rack-mounted equipment, in which case the cables can drop down from an open ceiling into the back of the rack assembly.
UTP cable is easy to install because it is thin and quite flexible. Other types of cable have different properties, however, that can make the process of pulling cable more difficult. 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. Therefore, it is possible to install this type of cable internally, but it tends not to bend around corners as tightly.
The biggest problem with an internal coaxial installation is the fact that Thin Ethernet networks use a bus topology. This means that you must pull one length of cable to each computer and then pull another length of cable from that computer to the next one. 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.
For more information about coaxial cable and the bus topology, seeLesson 1: Network Cables, in Chapter 2, "Network Hardware."
Thick Ethernet networks use RG-8 coaxial cable, which is nearly half an inch thick and very inflexible. This type of cable is hardly ever used today, but even in its heyday it was rarely installed internally. The main advantage of Thick Ethernet to the cable installer is that each computer uses a separate cable that connects the network interface card (NIC) to the main RG-8 trunk. Therefore, only one cable has to protrude through the wall.
Pulling fiber optic cable is roughly similar to pulling UTP. The multimode fiber used for most LAN connections is reasonably flexible, but because of the nature of the medium, the placement of the cable must be more precise with respect to the bend radius as it turns around corners. One advantage of fiber optic cable is that it is immune to electromagnetic interference, so many of the obstacles around which you must normally route copper-based cables, such as fluorescent light fixtures, are of no consequence in a fiber optic installation.
It's a good idea to pull all of your cable runs before you begin making connections to wall plates and patch panels. This enables you to move cables as needed and bundle them together before they are permanently affixed. When you perform an installation this way, however, you must be careful to label all your cables at both ends, so that when you make your connections, you're certain which cable you're holding.
After all the cables are pulled, you're ready to begin making the connections. This process is discussed in the next lesson.
For each of the following network scenarios, state whether you would perform an internal or external cable installation, and give a reason why.