Broadband

10 things you shouldn't do when running network cable

Improperly installed cabling can cripple network performance, create maintenance headaches, and lead to hidden costs. Here's where things can go wrong.

Network cabling can be a finicky thing. There was a day when people without appropriate knowledge and training were tasked with running cable by virtue of their other responsibilities. For example, telephone techs and electricians used to be tapped because they were cabling people. However, while telephones cables can sometimes tolerate quite a lot of error, data cabling is less forgiving. I'm focusing here on twisted pair cabling, not fiber. Here are 10 mistakes to avoid when you're installing network cable.

Mistake 1: Not planning for the future

Perhaps your organization has provisioned 100 Mbps network connections to the desktop for now, even though 1 Gbps has become pretty standard. But suppose your organization is going to move to a new location and you need to install new cabling. Are you going to go with yesterday's best cabling technology or are you going to install something that will meet today's needs and your needs for the next few years? Remember, the labor is the most expensive part of your project. While top-of-the-line cable won't be the least expensive option, you should consider reasonably high-end cable for your installation. Maybe you don't go with the absolute best -- after all, many organizations won't need 10 Gbps to the desktop for quite some time -- but don't go for cheap, either.

Mistake 2: Using different cabling for voice and data

Twisted pair cabling used to be expensive, so companies used to install different cabling for voice and data needs. Since voice was a less picky service and required only a single pair of wires, less expensive cabling was used for voice while data enjoyed the bulk of the budget.

Today, a complete installation can still be pricey but the bulk of the cost is generally labor; cabling itself really isn't a massive cost. Further, with the rise of services such as VoIP, voice in many places has transitioned to being a data need and requires data-level cabling. In fact, with the right VoIP equipment, you can often get away with using an existing data cable and then making use of the VoIP device's built-in Ethernet switch to save on the cost of running multiple cables, if that becomes absolutely necessary.

The point here: Don't simply assume that you can or should use old style category 3 cabling for voice. If you're going to run a separate cable for a phone, match the data cable type.

Mistake 3: Not using cable management

Adding cable management is often seen as a "would be nice if" type of scenario. Adding ladder rack, rack-based cable management, and the like does add cost. But it also makes ongoing maintenance much, much easier. Bear in mind that the cabling work won't stop with the initial installation. More cables will be added, and things will be changed. Make sure that you label appropriate cables, color-code cables, or implement some other kind of process to make it easier to identify cables later on.

Mistake 4: Running cable in parallel with electrical cables

Data cabling used "UTP" -- unshielded twisted pairs -- to achieve its goals. The magnetic field generated by the low voltage running through the cable is a critical component of the communications chain. When you run this unshielded cabling in parallel with electrical cables, that magnetic field is disrupted and the communication becomes noisy and garbled. In many cases, transmissions will simply not make it from Point A to Point B. In other cases, transmission rates will slow to a crawl as communications are constantly retried.

If you have to go near electrical power lines, cross them in perpendicular instead.

And now for a story: Way back in the late 90s, I was asked to look into why a newly installed coaxial cable wasn't working. It was a building-to-building connection between two buildings that were very close to one another. Upon arriving at the site, I looked up and saw that the coaxial cable was twisted around the overhead electrical cabling that ran between the two buildings. Needless to say, it was easy to identify the cause of the problem.

Mistake 5: Running cable near "noisy" devices and fixtures

Noise can be introduced onto data cabling by more than just electrical wires. Fluorescent lighting, motors, and similar items that shed electrical or magnetic interference will wreak havoc on your cabling infrastructure as well. Make sure that in your planning, you leave a data cable pathway that avoids these kinds of hazards.

Mistake 6: Not minding distance limitations... to a point

If you've run any cabling at all, you know that the typical distance limitation for UTP cabling with typical Ethernet -- up to 1 Gbps anyway -- is 100 meters. However, if you're running cabling for some other purposes, such as 10 Gbps or 40 Gbps, be mindful of the distance limitations associated with the type of cabling you intend to use. For example, if you intend to run 10 Gbps for up to 100 meters over twisted pair cabling, you need to use Category 6A or better cabling.

Mistake 7: Not following laws/codes/ordinances

This is really important for many reasons. First of all, failure to adhere to local codes can create dangerous issues for safety personnel. For example, in most places, use of PVC-jacketed cabling is prohibited in air handling spaces. When PVC burns, it creates a toxic stew that can be harmful to firefighters and other personnel that might have to navigate the area in the event of an emergency.

If you fail to follow local codes related to low voltage cabling, you risk fines and may even have to rip and replace your cabling. So make sure you verify your responsibilities before you get started and make sure that any contractors you have working with you are aware of local ordinances as well.

Mistake 8: Not testing your cabling infrastructure

Once the cabling is installed, you should test every cable using appropriate tools to make sure that it will be suitable for its intended use. This includes verifying length and cable specifications matched to needs. If you need 1 Gbps transmission speeds, verify that the cable's properties will support that need.

Mistake 9: Not following standards

You know, there are only eight individual wires inside a cabling jacket. So why not just terminate them at random, as long as you use the same scheme at both ends and you're consistent between cables? Well... that's a bad idea. There are standards in place for a reason. The cabling standards take into consideration just how the cables are twisted and placed in the jacket. If you deviate from those standards, you risk introducing noise and inefficiency into your cable plant that can have a negative impact on overall network performance. The standards I speak of are known as EAI/TIA-568-A and B and dictate the method by which data cables should be terminated.

Mistake 10: Not running a cable when you need one

Recently, my colleague Erik Eckel wrote about the dangers of using an Ethernet switch when a new cable run is really what's needed. When you start adding Ethernet switches willy-nilly, you risk introducing unknown elements and instability into an otherwise well-designed network. In general, people use mini-switches when they just need to add a port or two, so there is very little traffic planning undertaken. Depending on the reason behind the need for the additional ports, this can be problematic. If the new services require a lot of network resources, you can create bottlenecks where you didn't intend to. The lesson: Unless you have a really good reason not to, just run another cable (actually, run two; the cabling is cheap but the labor is similar).

About

Since 1994, Scott Lowe has been providing technology solutions to a variety of organizations. After spending 10 years in multiple CIO roles, Scott is now an independent consultant, blogger, author, owner of The 1610 Group, and a Senior IT Executive w...

31 comments
johnkarter87
johnkarter87

Good job!! must say.. Thanks for sharing this information. It would help me a lot in assembling my cables. Would you please tell me should I use one cable for Voice and data or use of different cables doesn't harm?

robert key
robert key

nice information you explained everything step by step

peterlamonica
peterlamonica

Pulling cable is a two person task. If you pull cable without someone feeding it you will wind up with kinks in the cable effectively destroying the entire run.

lordbrayam
lordbrayam

Very good article, and indeed must plafinicar good wiring and think ahead, not only the basic needs of the present, as these increase significantly. eg "Data Cabling" is something that increases every day by new technologies and the use of more data.

Tromman
Tromman

I was called in to find out why a new building with new cabling was simply not working over any part of the network. The cabling had been done by the local telecomm team. Beautiful conduits, very neat wall plate connections BUT when I took a look behind the patch panel I find ..more very neat work. Each cable had been straightened and lined up with its partner along a board and pinned in place. Then nice right-angled turns into each port. Pretty but all the cables were untwisted for at least 24 inches! I had to move the rack to get enough cable to re-terminate the panel properly. I can just imagine the 'phone tech guy with the guys having a beer after work... "the cable they gave me to work with was terrible, all twisted to hell! "

kylehutson
kylehutson

Run *4* instead. Somebody will certainly want a VoIP phone, network printer, and spare laptop connection there in short order. Seriously, cable is cheap in comparison with labor. Even if you just label it and leave it unterminated, I've never regretted running too many cables.

kylehutson
kylehutson

On #1 - if you're doing new construction (and you have any say in the matter whatsoever) - use conduit! Having done more ThinNet to Cat3 and Cat3 to Cat5, and even a Cat3 to Fiber (yes, prematurely) than I would like to admit, trust me, the cost of the conduit will pay for itself many times over.

Chilidog67
Chilidog67

One thing I run across a lot in bad UTP installs is punch downs with way too much of the cabling untwisted at the end. They are intended to be punched down snugly, you shouldn't have 1 or 2 or 6 inches of untwisted wiring - it violates the integrity of the cable completely. Also, ditto on the testing and marking of the cables. It's great to follow a standard (if you don't, get one) but if you don't have one at least mark it unique and the same at both ends.

abdulrahman.alrashdan
abdulrahman.alrashdan

Always wait for the FINAL furniture layout, usually you will get 4-5 blue prints before they make their mind. dont forget the Printer, WiFi, Projector, Fax Machine, and the kitchen if you have IPT, forthe drawings and documentation, keep a copy in the cabinet, one with the network admin and one for the facilitymanagemnt team.

a.portman
a.portman

Mark both ends and then write down someplace where (room/floor) the drops are. Five years from now someone else may be looking at the panel wondering where 231 is, because it isn't in room 2-31.

jcitron
jcitron

Way back in my old days in IT, I worked for a company that used both Thin-net and older Thick-net cabling. This cable was awful to run and maintain. I, and probably many other people, welcomed the change over to UTP when that became the standard much later on. When I started my job there, they had me run cabling for their demo room. I was a tech, but this was my job too because I was the new guy. There were network problems all over the building. As I worked my way through the mess, it turned out to be self-inflicted by my tech teammates. They had insisted on running the thin-net cable over the florescent light fixtures, which were causing all kinds of poor performance due to electrical interference. I explained to them what the problem was, but they insisted I knew nothing because I was the new guy on the team. Then there were the vampire taps and the Thick-net cable. This nasty stuff has its own issues such as bending radius and tapping too deep into the coaxial cable. The standards are set to ensure proper data handling and good performance. Well again these guys insisted on shoving this cable into tight spaces, which bent the cable too tight. There were also other cases where the taps were obviously too deep into the cables, which had to be replaced. When I mentioned this too, I was told to shut up and do the job. I didn't last much longer with them after that, and left for a much more respectful company. The org closed a few months later when they were purchased by another company and everything was transferred to Delaware.

psychobyte
psychobyte

I know spreadsheets are popular for documenting patch panels but, does anyone know of more advanced software for documenting your patch panels, switches, etc?

oskar401
oskar401

Another common error is to over-cinch cable ties on bundled cables, specially on racks. Use a good tension tool that provides repeatable results. Over-tension can throttle bandwidth significantly

rkendsley
rkendsley

If cabling in a building with more than one story, then cabling rated for air ducts (plenum cabling) should be used for the lower level even if the cabling is not routed through air ducts. If a PVC jacket on a cable were to burn on a first floor, then the toxic chemicals could rise up to the second floor level and above. Note: The space between the buildings structural ceiling and a suspended ceiling is usually considered a plenum air space (This applies to raised floors in computer rooms as well). Caveat: Some ceilings create a tight seal with no air flow, so are not subject to these restrictions. Additionally, some new theories suggest that abandoned cables in plenum air spaces may create a hazard in the event of a fire since the air flow through the spaces supplies oxygen which will fan the flames and create a much hotter and stronger fire.

Ray Baker
Ray Baker

Line that reads: If you have to go near electrical power lines, cross them in parallel instead. Should be perpendicular, not parallel.

catcinq
catcinq

"If you have to go near electrical power lines, cross them in parallel instead." not sure "parallel" was the intention

TBone2k
TBone2k

#8 That means using a cable testing device, such as a LANcat, or other device to certify the connection. Not using an LED tester to show the wires are right and then plugging in a computer and checking if it shows a 1Gb connection. Also the real testers will generate a log which the installer can give you to show everything was done. #3 and #9: In order for network cable runs to be certified, they must also be terminated with a jack at each end, not just left with an RJ45 end to plug into the switch/computer.

Realvdude
Realvdude

We moved into an office space already wired for phone and network. Tucked behind one of the patch bays was a floor plan with jack identifiers.

armitsteadt
armitsteadt

Absolutely spot on! Always map and document it in detail, and put copies in several places with a name beginning with an "A" or zero so it can be found easily at the top of the relevant folder. In addition, I also write the specific floor/room number on the top edge of the door on a bit of masking tape (it's the one safe place guaranteed not to get disturbed.) May be overkill, but the doc will then always match up should there be any later room renumbering.

Papa_Bill
Papa_Bill

you might damage the cables by inserting your cutters too far into the bundle.

GreatZen
GreatZen

PVC cables also serve to allow the rapid transport of the flame from a central location to an entire building, often in under a minute. A key factor in plenum cabling isn't just the minimal toxicity of the fumes, it's the fact that the jacket is self-extinguishing.

Scott Lowe
Scott Lowe

Thanks for pointing this out... it'll be corrected.

DuhGreek
DuhGreek

I think "perpendicular" was intended, no?

Scott Lowe
Scott Lowe

Wow... I didn't know that... another very god reason to choose Plenum over PVC. Thanks! Scott

Scott Lowe
Scott Lowe

Absolutely. I'm the author... I certainly meant perpendicular.

Papa_Bill
Papa_Bill

It seems to me though that since most interior power cables are in conduit that emi wouldn't be that much of a problem. I've seem hundreds of feet of telephone lines run alongside power conduit with no interference problem. (remember, that's UTP analog and highly susceptible to emi.)

nwallette
nwallette

Cross at an angle, then keep a few inches or more between high and low voltage.

MikeGall
MikeGall

I'm not sure but I think often there are chutes running parallel with hallways where the power is run, and of course it is easy to run along a drop ceiling that way. If you are trying to cross perpendicular wouldn't you have to do some weird things? Ie. run the wires across every wall, if you are running data chutes than you'd have to make a gap in the chute where it crosses power etc. Fortunately I don't have to do network monkey work but for those that do ... ease the pain :-)

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