Cat6 cable speed question

Willie5002 · 18 May 2025 at 17:44

Good day,

My name is Willie and I am new to this forum.

I have a question regarding Cat6 cabling, which I hope some member could assist with shedding some light on and apologies if this has been answered before.

I recently bought two rolls of Cat6 cabling from two different manufacturers. When I made a 8-wire RJ45 patch cable (with straight connections (and all wires in pin to pin format)) from the two rolls of Cat6 cabling, I found that both the patch cables (with straight connections) I made from the two rolls of Cat6 cabling are capped at a speed of 94Mbps, but a pre-made Cat6 patch cable (with the same straight connections configuration) I bought from a store would provide around 980Mbps. All three above-mentioned cables test exactly the same in terms of pin connections, when testing them with an Ethernet cable tester.

When I queried this with the supplier, I was told that I have to use the cable in a 8-wire crossover format (two wire pairs (green and orange pairs) crossed over on one end of the cable (basically wiring the cale according to theT568A standard at the one end of the cable and wiring it according to the T568B standard at the other end of the cable)). I subsequently made another two 8-wire crossover cables from the same two rolls of Cat6 cabling and found that the Cat6 crossover cables now provide speeds of 980Mbps.

My question is: Why would the cables I made from the two rolls of Cat6 cable, when wired in patch cable format (with straight connections), only provide 94Mbps and the exact same Cat6 cable in crossover format provide 980Mbps, but a pre-made Cat6 patch cable (with straight connections) I bought from a store provide would around 980Mbps in the exact same application?

I believe that the rolls of Cat6 cable supplied to me are not of a proper Cat6 quality of cableling and that the pre-made Cat6 cable is made of a proper Cat6 quality cabling. Would a true Cat6 cable demonstrate this behavior, in that it can only provide gigabit speeds when connected in a crossover configuration?

I would highly appreciate it if someone could assist with clarifying this.

Thank you in advance.

ChrisD. · 18 May 2025 at 19:57

Straight through/cross over doesn't matter these days, the vast majority of switches will recognise it. What are you testing with? Just cable straight, the days of requiring cross over are long gone unless you have some really old hardware. Not to mention the link probably wouldn't even come up. Hence I think it might have been an issue with the crimping, poor cables, or poor heads.

Willie5002 · 18 May 2025 at 20:34

ChrisD. said:
Straight through/cross over doesn't matter these days, the vast majority of switches will recognise it. What are you testing with? Just cable straight, the days of requiring cross over are long gone unless you have some really old hardware. Not to mention the link probably wouldn't even come up. Hence I think it might have been an issue with the crimping, poor cables, or poor heads.

Thank you for your reply. I connected an Android tv box to a gigabit network switch. When I connected the pre-made straight through cable between the switch and the tv box, it provided a speed of 980mbps. When I made four straight through cables which were the same lengths as the pre-made cable from the roll of Cat6 cable, I purchased, all of the cables I made only provided me with a speed of 94mbps. When I cut off the RJ45 on the one end of the cables I made and changed the configuration on this one end to a crossover configuration, the cable provides a speed of 980mbps. I really do not understand this.

Zefan · 18 May 2025 at 23:21

Sounds like something chinesium (android box) might still somehow be fussy and not have/have rudimentary auto mdix. The way to confirm this would be to test your straight cables with other devices.

Just to confirm, definitely using the T568 pinout standard on the straight through too?

Willie5002 · 19 May 2025 at 08:04

Zefan said:
Sounds like something chinesium (android box) might still somehow be fussy and not have/have rudimentary auto mdix. The way to confirm this would be to test your straight cables with other devices.

Just to confirm, definitely using the T568 pinout standard on the straight through too?

Hi, thank you for your suggestion. I performed the same test by connecting a Huawei AX3 Router and a Zyxel EMG3525-t50b configured as access points and also found that the Cat6 straight cables I made, configured according to theT568A standard on both ends, were capped at 94mbps and the crimped crossover cables I made, configured according to theT568A standard at the one end of the cable and wiring it according to the T568B standard at the other end of the cable, and found that this same Cat6 cable configured in the crossover configuration yielded speeds above 600mbps. When the purchased straight Cat6 cable configured according to T568A on both ends also yielded speeds of above 600mbps. Does this mean that the Cat6 cable supplied to me is of an inferior quality?

ChrisD. · 19 May 2025 at 08:50

I'm confused, you should be using the same standard at both ends of the cable, don't waste your time doing cross over cables.

Avalon · 19 May 2025 at 09:10

No matter how good the cable, if your termination sucks, it sucks. That said, you said rolls, are we talking 305m here? Because the spec won't allow gigabit over that, you also need to consider bend radius and what it's routed next to, eg not mains cabling.

Armageus · 19 May 2025 at 09:20

Willie5002 said:
When I made a 8-wire RJ45 patch cable (with straight connections (and all wires in pin to pin format))

Define what you mean by this? (as it sounds like you aren't following a standard and just doing any pins as long as they are the same at each end)

If you aren't following the same T568A or T568B at both ends and are doing something different then you will likely end up with only 2 pairs and 100Mbps speed.

picnic · 19 May 2025 at 09:27

Armageus said:
If you aren't following the same T568A or T568B at both ends and are doing something different then you will likely end up with only 2 pairs and 100Mbps speed.

This

Caged · 19 May 2025 at 10:55

The 100mbps link speed when you wire the cable one way vs. the 1000mbps link speed you see when you wire it as a crossover has nothing to do with the crossover part, it's that you're making the cable wrong.

Take a clear photo of each terminated end and people will be able to point out any issues.

Meddling-Monk · 19 May 2025 at 11:38

There's also the small possibility that you might have solid core copper Cat 6 cables there, and when you are attempting to crimp on the ends when you make it yourself, you're using the wrong plugs. Some only work with stranded copper, whilst others work primarily with solid core copper cables. So there might have been a possibility that it just happens to work with straight connection, but the crossover just happens to have had a bad connection because of the wire difference and the plug didn't/couldn't bite onto the wires due to them being made for different types.

bledd · 19 May 2025 at 17:41

Take photos of the ends, multiple photos and show them here.

They'll either be miswired or badly crimped.
Cat5e can do 10000 mbit.

Willie5002 · 19 May 2025 at 19:32

Thank you for all the comments.

Below is a picture of the three Cat6 patch cables I have and used for the speed tests. The blue cable at the top of the picture is a straight through pre-made Cat6 cable I purchased. The first grey cable directly below the blue cable in the picture is a crossover cable I made. The grey cable at the bottom of the picture is a straight through cable I made.

https://www.pinterest.com/pin/1115415032718106496/

Picture of the straight through wiring on the blue pre-made (purchased) Cat6 cable providing a max speed of 980mbps

https://www.pinterest.com/pin/1115415032718106501/

Picture of the crossover wiring on the grey Cat 6 cable I made (cable directly below the blue cable in the first picture), providing a max speed of 980mbps (I made three of these crossover wired cables an all three provide the exact same speed)

https://www.pinterest.com/pin/1115415032718106503/

Picture of the straight through wiring on the second grey Cat 6 cable I made (cable directly below the blue cable in the first picture), providing a max speed of only 94mbps (I made three of these straight through cables an all three provide the exact same speed)

https://www.pinterest.com/pin/1115415032718106508/

The grey Cat6 cables were made from 50cm long pieces cut from a 500m roll/drum of Cat6 cable to test the speed of the cable, prior to installing long runs and have the following printing on it:

https://www.pinterest.com/pin/1115415032718107039/

In my tests only the three Cat6 cables were changed/switched between the network switch and the device connected when the speed tests were conducted.

I am still at a loss why the Cat6 straight through wired cables I made only provides a max speed of 94mbps, but the same Cat6 cables wired in the crossover configuration provides a max speed of 980mbps and the purchased pre-made straight through wired Cat6 cable (blue cable in the pictures) can provide A max speed of 980mbps. I also used connectors from the same pack of connectors purchased.

bledd · 19 May 2025 at 20:31

Upload them to Imgur, can't see those. There's no need to make crossover cables. They were from pc to pc back in the day, not needed now.

Sone · 19 May 2025 at 23:34

Something very wrong. I wired my house in Cat5E many many moons ago. I upgraded to 10gbE switches expecting to rewire but no 10gb worked perfectly on old cat5E cable

Willie5002 · 20 May 2025 at 07:47

I am trying again to make the photos I took available and re-post my previous message, with the images shared via Imgur.

Below is a picture of the three Cat6 patch cables I have and used for the speed tests. The blue cable at the top of the picture is a straight through pre-made Cat6 cable I purchased. The first grey cable directly below the blue cable in the picture is a crossover cable I made. The grey cable at the bottom of the picture is a straight through cable I made

Picture of the straight through RJ45 wiring on the blue pre-made (purchased) Cat6 cable providing a max speed of 980mbps:

Picture of the crossover RJ45 wiring on the grey Cat 6 cable I made (cable directly below the blue cable in the first picture), providing a max speed of 980mbps (I made three of these crossover wired cables and all three provide the exact same speed):

Picture of the straight through RJ45 wiring on the second grey Cat 6 cable I made (cable directly below the blue cable in the first picture), providing a max speed of only 94mbps (I made three of these straight through cables and all three provide the exact same speed):

The grey Cat6 cables were made from 50cm long pieces cut from a 500m roll/drum of Cat6 cable to test the speed of the cable, prior to installing long runs and have the following printing on it:

In my tests only the three Cat6 cables were changed/switched between the network switch and the device connected when the speed tests were conducted.

I am still at a loss why the Cat6 straight through wired cables I made only provides a max speed of 94mbps, but the same Cat6 cables wired in the crossover configuration provides a max speed of 980mbps and the purchased pre-made straight through wired Cat6 cable (blue cable in the pictures) can provide A max speed of 980mbps. I also used connectors from the same pack of connectors purchased.

ChrisD. · 20 May 2025 at 07:51

You are not wiring to T568A or T568B standards.

Step-by-Step Guide: How to Terminate Ethernet Cables?

People often buy a patch cable to plug into the port of a router or computer. But why not DIY a patch cable yourself? Here is the easy guide for network beginners.

www.vcelink.com

First link I found, plenty of other guides.

Pick either A or B, and use the same standard at both ends. It makes no difference which you choose, I personally prefer B just because it's how I was taught 20+ years ago when I did structured cabling.

Armageus · 20 May 2025 at 08:09

Willie5002 said:
I am still at a loss why the Cat6 straight through wired cables I made only provides a max speed of 94mbps

Because they aren't wired correctly - you can't just pick any old colour scheme and then wire them the same both ends.

Edit:
Your crossover works, as it's wired correctly - T-568B on the right hand side, and T-568A on the left hand side. As most network devices are auto MDI-X, they will detect a crossover cable and switch themselves to work as if it was a normal cable - hence full Gigabit speeds.

bledd · 20 May 2025 at 08:36

Do them all as 568B. Only press down once on the crimper, check that the wires all reach the end of the pins

Caged · 20 May 2025 at 09:45

I'm really confused how you managed to get the wires in the right places for a crossover cable but haven't stuck to any known standard for your other cable.