First of all if anything goes wrong set your network settings to automatic again.

Before we begin, make sure this will work for you. Some connections wont get a speed boost at all.

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It is from Google and there's no viruses, download it and run it.

Open it then click start.

Give it a few minutes, when its done it will pop up and tell you if your eligible for a speed boost.

Once its finished if you see a screen popping up saying that Their DNS is faster than yours, you're in luck.

Now, use those DNS on the side for Xbox. To do that, go to network settings, click on DNS, and make it manual then set it to the numbers Provided.