We Just Installed Cat6 Cable So Why Is the Network Running Slow?

We Just Installed Cat6 Cable So Why Is the Network Running Slow?

Welcome to a customer issue troubleshoot with Don Schultz, our technical lead.

Last month, trueCABLE received a help request from a customer who had purchased 1000 feet of our Cat6 Direct Burial cable.

For those new to outdoor installations, direct burial rated cables don’t need conduit for outdoor installation and can withstand harsh conditions like groundwater, temperature extremes and sunlight due to added weather-proofing.

Outdoor rated cables with polyethylene (PE) jackets can operate in temperatures up to 75°C (167°F) and down to -40°C.

Customer Question

We made three 200’ cable runs, but all 3 show a different length (13’ shorter) on the blue pair and will not transfer data at 1GB/sec. We also noticed the blue pair and green pairs are not twisted as tightly as they should be. Is trueCABLE able to resolve this situation? Cat6 typically has twists above 2 twists per cm. The blue pair has less than a single twist per cm, and the green pair has 1.2 twists per cm. The 600’ we’ve installed will need to be removed as it does not meet our network requirements. I would like to return the unused portion of cable for a new 1000’ roll that does meet the Cat 6 specs of at least 2 twists per cm on all pairs.

Don's Response

I’m sorry to hear that you are having trouble reaching 1G speeds on the cable. This cable should be able to reach that speed without breaking a sweat.

I read your concerns around the twists of the blue and green pairs. These pairs are not twisted as tightly as the brown and orange pairs and this is by design. The ANSI/TIA 568 C.2 specification does not indicate how many twists an Ethernet cable must have to classify into a particular Category. What determines the Category of a cable is the performance attained at 295 feet (89.9m) or 328 feet (99.9m) depending upon whether we are talking about Channel or Link Certification on a Fluke test.

Cable performance is affected by:

  1. Jacket thickness
  2. Conductor thickness
  3. Conductor insulation thickness
  4. Spline presence
  5. Twists per inch on the pairs
  6. Shielding or lack thereof

I'm assuming that you have double-checked how your runs have been terminated, and the compatibility of your termination hardware--keystone to keystone or RJ45 to RJ45, as this could impede performance. Also, are the cables run within either 16" of any typical EMI/RFI source such as 120V electrical wire, fluorescent light fixtures, or 48" to high voltage sources such as 240V or higher cabling, electrical panels, electrical motors? Both of these scenarios will disrupt signals. Finally, how are you testing signal speeds? Are you using a multimeter? This will help clarify how you are getting your results.

For the sake of other readers and to help identify what you may be seeing, let’s take a deep dive into some of the things mentioned in your email and explore why you may be having issues.

Things to keep in mind when deploying Cat6

1. Does the cable Category match the capability of the network equipment?

Cat6 cable supports up to 10 Gbp/s. When transmitting at 10 Gbp/s, however, the cable only supports 37-55 meter runs. The higher the level of crosstalk, the shorter the distance. Slower speeds, like 1 Gbp/s, transmit the full 100 meters.

Cat6A is constructed differently, which more effectively eliminates alien crosstalk (AXT). If AXT is your issue, consider upgrading.

2. Have the terminations been inspected and re-terminated if necessary?

Usual suspects are nicked conductors, and excessive untwist of the conductors. Cat6 sheathing guards against near-end crosstalk (NEXT) and alien crosstalk (ACT), so other factors than the cable itself may be contributing to signal interference.

3. Is there any electromagnetic or radio frequency interference (EMI/RFI) in the environment that would affect the cable at any point along its length? Is shielded cable necessary in this situation?

The usual suspects here are electrical, heavy machinery, or high EMI environments like hospitals with medical equipment. If you’re using unshielded cable, do you need to switch to shielded? In that case, it might be simpler to simply reroute the cable and the endpoints to a different location.

4. If shielded cable was used, are there any ground loops or floating cable shields?

Ground loops occur when multiple AC feeds (called mains) are involved. If the cable is running in the same or between structures with more than one AC main, be sure grounding occurs at a single end only.

Floating cable shields are due to lack of grounding at all, which occur from not using shielded connecting hardware so the cable shield can make continuous electrical contact and therefore drain off to ground.

5. Is the network equipment operating properly?

Check to see that your switches don’t need firmware updates or have reached the end-of-life (EOL) and are beyond the window of manufacturer updates or maintenance support and ready for replacement.

6. Do all patch cables used in the chain match the speed and type of the permalink links installed?

We’ve all been there. It’s critical to go through your full chain because one device or connector can impact the rest of your network.

Final thoughts on troubleshooting network speed issues

Keep in mind that when working in a shared space with multiple tenants, things happen externally to your equipment affecting the performance of your network.

Noise on the other side of your server room wall or near an outdoor kiosk could directly impact the signal strength. That’s it for now. Drop a comment below to let us know of troubleshooting tips or experiences you’ve had along the way. We’d love to hear from you.


 trueCABLE presents the information on our website, including the “Cable Academy” blog and live chat support, as a service to our customers and other visitors to our website subject to our website terms and conditions. While the information on this website is about data networking and electrical issues, it is not professional advice and any reliance on such material is at your own risk.

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