2 Xbox one's on the same network can't connect to Xbox live servers at the same time.

Hey there Cullen Q,

Thanks for reaching out to the Forums for advice on how to deal with this issue. I can totally see how this could bamboozle anyone. I think it would be best to troubleshoot the network that you're connecting to. Try power cycling the console's after you
have reset your router.

When you get the chance, try the steps outlined on our site
as well and let us know if that helped.

Thanks for reading!

Yes, two consoles with separate xbox accounts with gold and separate copys of the game.

There are Two Xbox ones on my network and only one can access Xbox live servers for Modern Warfare at once. One will get on just fine then the other one will keep failing to connect to Xbox live servers until the other console gets off. What can
be done for this?

Do you 2 copies of Modern Warfare and a separate gold account for each console?

We have two Xbox's and we play fine online and with Modern Warfare.

This would be blatantly false, The device that is connected to xbox live is irrelevant in this case, as xbox one, and scarlett will all be on the same xbox live network/server. The only way your day one xbox one would lose access to xbox live is if they
perform another xbox live rollover like they did with the generation 1 era games (halo/halo 2. etc)

Not all routers can do it.

I know for a fact that my d-link can connect two 360's both with open NAT.

Link to router