Ethernet Cables: Cat-5 vs. Cat-6

Those of you who have been following my blog know that I love to write about what I classify as the soft sciences. By that I mean protocols, call flows, software, security, and other technologies that are for the most part, hardware and infrastructure independent. Does it make much difference if I run a SIP stack on a PC, virtual server, or smart phone? Not really. SIP acts like SIP no matter what platform is sending or receiving it.

So, it may come as a surprise that today I am writing about something that has little to do with source code or security certificates. I want to espouse on Ethernet cables.

Honestly, I didn’t give cabling a lot of thought until last week when I was speaking at an Avaya Users’ Group meeting in Tampa, Florida. After the president discussed old and new business, he opened the floor to the members to ask questions of their fellow Avaya users.

The questions were good. I took notes on several and chimed in where I felt I had something to add. However, the one that I found most interesting was this, “We are in the process of redoing our building’s LAN cables and I was wondering if people are installing Cat-5 or Cat-6.”

The answers varied quite a bit. Some folks already made the switch, a few decided not to, and some fell into the not-sure-what-we-will-do category.

For those of you who don’t have a plan (and I will assume that many of you are in that camp), allow me to spend some time introducing you to the Cat-5, Cat-5e, Cat-6, and Cat-6a Ethernet cables.

But first, this handy-dandy comparison table.


Length (meters) 10 Mb/s 100 Mb/s 1 Gb/s 10 Gb/s Power Over Ethernet Frequency in Mhz
Cat-5 100 X X X 100
Cat-5e 100 X X X X 100
Cat-6 100 (55 for 10Gb/s) X X X X X 250
Cat-6a 100 X X X X X 500


The Differences

As the class of cable goes up, so does the speed and frequency of the wire. The biggest difference between Cat-5/5e and Cat-6/6a is the speed. Cat-5/5e tops out at 1 Gb/s and Cat-6/6a allows speeds up to 10 Gb/s.

The difference between Cat-6 and Cat-6a is that Cat-6 is only guaranteed for a distance of 55 meters at 10 Gb/s. Cat-6a can run at that same speed for up to 100 meters.

Physically, Cat-5/5e and Cat-6/6a differ in a number of ways. First, there are more twists per centimeter of wire in Cat-6/6a. Cat-5 and Cat-5e typically uses 1.5 to 2 twists per centimeter and Cat-6 and Cat-6a uses 2+ twists per centimeter. Twisting reduces interference between internal and external wires.

Second, Cat-6/6a use a thicker outside sheath than Cat-5/5e. This sheath protects against near end and alien crosstalk. Crosstalk is more likely as the frequency (Mhz) increases. Cat-6 and Cat-6a support higher frequency ranges so they have the thickest sheaths.

Lastly, a nylon spline (a longitudinal separator in the wiring) can also be used to reduce crosstalk. Cat-5e always has a spline, Cat-5 sometimes has a spline, and depending upon the manufacturer, Cat-6/6a may also have a spline. Since Cat-5e requires a spline and Cat-5 does not, Cat-5 has a thicker outside sheath than Cat-5e.

Cost-wise, Cat-6 and Cat-6a are about 10 to 20 percent more expensive than Cat-5/5e. So, cost is not a big issue considering the fact that you can obtain speeds ten times faster when you go to Cat-6/6a.

It’s important to know that Cat-6 and Cat-6a are backwards compatible and can be used with older Cat-5, Cat-5e, and even Cat-3 equipment.

Should You or Shouldn’t You?

If it were me, every new installation would use Cat-6a wiring. Running cable through a building is an expensive proposition and since most cable will stay in place for up to 10 years, I would future-proof my company by adding the fastest option available whether I was ready to rollout 10 Gb/s or not.  Running cable twice in a short amount of time would be very foolish

However, I would not pull out perfectly good Cat-5e cable if I wasn’t ready to move to a higher speed. Wait until you need it before spending the money. Besides, by that time, there may be something even better that you can run.

Mischief Managed

This is an important topic that may not jump out at you as you look at upgrading your network switches and routers. However, as you saw, cable choice can make the difference between lightening fast and yesterday’s speeds.

Notice that I didn’t mention Cat-7 cables. For some folks, Cat-6a is ancient history. However, that wasn’t the original question and I need to leave myself something for a future blog article. Stay tuned.


  1. Glenn Reed · · Reply

    Excellent article Andrew, you have captured the topic very well and have a solid recomendation. Thanks for continuing this discussion from our chapter meeting. One caveat that I would mention on Cat5e is that, as you state, it is rated for 1 Gb/s which is very comon for PC’s and IP phones to use these days; however, with that being the high limit many other factors could degrade the capacity of installed Cat5e brining its performace capability below the stated max. Things like the quality of the installation (propper bend radius, propper mounts in the ceiling and floors, not installing too close to HVAC equipment, AC system, etc.) and the current condition of the cabling can have an effect on its performance…Glenn Reed, Tampa Bay IAUG.

    1. Excellent points, Glenn! Thank you for sharing.

  2. Wow, I had no idea that Cat-6 cables are the only ones that can transmit data at over 10 Gb/s! That is definitely a lot of power right there. In fact, I would have to agree that any business that uses computers should have Cat-6 to ensure that Internet speeds stay high at all times. Plus, if you are connecting a lot of computers to one router, it would probably be important to have Cat-6 to ensure that no one computer’s speed is throttled.

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