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).


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...

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