Ethernet not working, WiFi works

[mougu]

I have Gigabit Fios and my ethernet seems to work selectively. It works perfectly for most web services, but is extremely slow on a few of the sites that I frequent (Youtube, Netflix, and Gmail). When I switch my computer over to WiFi instead of ethernet, the problematic sites work normally. 

Other people on my network who are also on ethernet have no problems on their end. This makes me think that this is an issue with some network setting on my device. I have already reset my network settings and the issue persists. I am hoping someone here has some insight into what the cause of the problem could be and how to solve it.

I should also note that this is a recent issue that started happening about a week ago. I've had the same service since October of last year and my ethernet has had no trouble until now. There was Verizon outtage in my area about a month ago and after that is when I started to notice this problem. I am unsure if that outtage is the cause, but it was an interesting coincidence...

[Cang_Household]

Do you have a WAN IPv6 address? If so, do wired devices have Intel network cards? If so, you need to configure special settings on Intel NIC because they have bugs.

[mougu]

Running ipconfig shows that I have an IPv6 address, a temporary IPv6 address, and a link-local IPv6 address.

My computer does have an intel network card. The model is Intel Ethernet connection i219-V. What settings should I configure my network card with?

[Cang_Household]

https://forums.verizon.com/t5/fios-internet/youtube-buffering-horrible-quality/m-p/919089#M88218 

[mougu]

I have disabled TCP IPv6 Check sum and the issue still persists.

[Cang_Household]

Do you have switches in between the computer and the router? If the switch also uses the Intel chip, you need to disable them all along the network path.

[mougu]

The network switch that I am using is a Linksys SD2005. I believe this does use an intel chipset. With my current physical setup, it is not possible for me to bypass the network switch and plug my computer directly into the router.....

This is the same network switch that I have been using since October of last year, and my ethernet was working fine up until a week ago. Shouldn't that eliminate the network switch as part of the problem?

[Cang_Household · Accepted solution]

No. VZ rolled out the long awaited IPv6 for selective customers recently. Some devices and adapters does not work with IPv6 (despite being a standard since 1999) or did not implement it correctly without knowing until now (because nobody bothered to test it).

[mougu]

Gotcha. I will see if I can find a way to connect my computer directly to the router and see if that fixes the issue.

[jcettison]

 I was having intermittent internet connection problems. The internet worked, but then it didn't. Most sites loaded, but some didn't. Pages would freeze, or stall, or require multiple refreshes to go through. 

Found this post, disabled IPv6 outright via my Verizon router's firmware admin page and suddenly everything is working right as rain again. Seems like the IPv6 rollout was the culprit, at least so far. Will update if needed.