NETGEAR R6700v3 hardwire connection slows down with CAT6 compared to CAT5e

[OneSpellWizard]

As the title says, I have a strange situation with my download speed. I'm paying for 1gbps (gigabit) from Wave. For each speed I list here, I have tested it at least 2 times each on fast.com, speedtest.com, and google's speed test.

I have factory reset my router and reupdated to the latest firmware. QoS is off (if I turn it on, it slows down the speeds).

• When I hardwire my desktop into my Arris Surfboard SB8200 modem with my 50 ft CAT6 cable, I get ~900mbps, which is great!
• After I plug in my NETGEAR R6700v3 router to the modem using CAT5e, and my CAT6 cable for my desktop I get ~200 mbps
• If I swap the Router -> Desktop connection to a CAT 5e cable, my speed tests jump to 800 mbps down.

Are there known issues if a different cable is used from modem -> router, and router -> desktop?

[plemans]

Some devices are more sensitive than others to sketchy cat 5e cables. I'd be guessing that cable is boarderline. 

[OneSpellWizard]

Thanks for the reply! Sorry if it wasnt clear, I swapped the CAT6 cable (which already was able to get gigabit speeds if desktop plugged directly to the modem) for a CAT5e cable between desktop and router. The modem to router CAT5e cable was unchanged.

[plemans]

Try factory resetting the r6700. after the reset, during the install process,make sure to leave qos, access control, parental controls, and traffic monitoring all disabled

[OneSpellWizard]

I did the factory reset and getting the same issue as before. Even with a CAT 5e cable, it's still ~200mbps slower  (~500-600 mbps) than a direct connect of the Desktop to the Modem (~800mbps)

[plemans]

How are you testing the speed?

[OneSpellWizard]

Each time I test I do

1. 2 tests on fast.com
2. 4 tests on speedtest.net
   1. 2 on Whitesky Communications LLC
   2. 2 on Ziply fiber or another server
3. 2 on Google Search's speed test

[plemans]

Have you tried downgrading the firmware a version or 2