Port Mirroring as dual NAT for Xbox Live

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I'd like to use 2 Xbox Ones on Xbox Live behind a single ISP (Comcast). My networking gear is Mikrotik and supports Port Mirroring.

Would mirroring (which I see is usually used for monitoring traffic) be a solution to "forward" ports to two devices?

My rough understanding makes it seem like each Xbox's network traffic would effectively be spamming the other Xbox (but it would just drop the inappropriate traffic, and be fine). If that understanding is close to reality, what would problems would it encounter (would they each start blasting a bunch of NAKs and throttling each other) and is there a way to mitigate?

owenfi

Posted 2017-02-27T05:43:38.673

Reputation: 103

Answers

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No, at best that would be useless.

Both your consoles have different MAC addresses (and different IP addresses), so they'd just ignore each other's traffic (just like things used to work in hubbed shared-medium Ethernet). And the switch in your Mikrotik already delivers traffic for the destination MAC to the correct switchport, so switch mirroring isn't going to help with anything anyway.

That said, I haven't actually used an Xbox myself, but it seems that it should be enough to have UPnP enabled for automatic NAT port forwarding?

user1686

Posted 2017-02-27T05:43:38.673

Reputation: 283 655

Yeah, UPnP should work. For some reason (without much debugging yet) it isn't putting its entry in the dynamic NAT yet, maybe I'll just reboot it a few more times until it does :) – owenfi – 2017-02-27T07:36:54.980

Sorry, this made sense, and now it doesn't make sense: I know they have different MAC + IP Addresses; this technique is actually banking on them ignoring traffic. What I'm hoping for is they each get a connection to the Xbox live server, and each appear as if the port had been forwarded to them (while ignoring the other one's traffic) vs. the normal configuration of NAT forwarding to a single box only. – owenfi – 2017-02-27T09:05:53.657

For incoming connections, that's definitely not going to work. For outgoing ones, port forwarding shouldn't be necessary at all? – user1686 – 2017-02-27T09:08:53.653

Okay, I guess for the incoming packets, they'd go to both boxes, each would think it was for them (which wouldn't really be true, and it'd result in some sort of "corruption") and they'd both try replying which would result in race conditions and other errors. – owenfi – 2017-02-27T21:56:02.020

Asked: 2017-02-27T05:43:38.673

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Active: 2017-02-27T06:29:55.547