A couple friends are having a LAN party of sorts multiple TVs multiple xboxs etc. we can all get online and onto the bo3 servers no problem we just can't seem to join any public matches with one another.. Is this a built in mechanism within the game? Or is this some glitch that needs patching?
After doing a lot of digging and some internal testing on my network I was able to determine the ultimate problem is/was ports needing some forwarding. There is one port I believe it was 3074 that was the culprit. Both xbox's wanted to for a lack of better terms fight it out for that port, and one would end up being the dominate xbox between them which would put them in a NAT state that moderate to high as far as the game was concerned. So for each xbox I set up a port forward each one, one increment up from the other. So none of them were fighting for the same port, this ended up resolving the issue and all is well now
You are having a networking related problem, it has nothing to do with the game. I can't walk you though all the steps to get it working because I don't know what router you have. You want to search google for the term "port triggering". You will need to set some rules in your router for the ports associated with Xbox Live.
You need a router that implements UPNP efficiently and port trigger ports needed for Xbox live and Black ops 3. Recently purchased a Netgear WND3700 which is connected to Virgin Media Superhub 2 (Modem Mode) and works perfectly now with two Xbox Ones playing in same game! Before was just using superhub 2 as my main router but did not work as apparently it has poor UPNP as could not get open Nat type with it on both Xbox ones and could not play in same game as one Xbox would get booted off!
Yaemish's answer is not correct.
Let me, as a server technician and support specialist, explain why.
CoD is not new to the modding scene, as you should've seen by now, and due to this, as with many other games, typically made by EA as well ((Like PvZ: Garden Warfare)), are heavily modded, and mechanics abused.
The most often abuse is "Dual Boxing" or "Double Stations". This is where a person who does not use mods, in such as SYS.Res or JTAG manners, either hires a friend, or buys a software program, or in some cases, neither, to farm his main accounts' characters.
Example: I'm about to play Bo3 with my brother. We are on 2 different XB1's. The server detects that there are 2 Xbox's connected to it with the same IP, and refuses to allow us to connect to the same public lobby. Why? Because for all it knows, we are guilty of the dualbox farming technique.
Why is Dual Boxing such an issue? It's not. Well, not to the gamer typically, but to a company with dollar signs as their pupils, profit goes down the tubes faster than the Virtual Boy because the P2W scheme is being circumvented by these "farmers".
Your best bet at this point is to re-wire to connect one to cellular data, or connect through LAN to a PC, and run it through a proxy or VPN, so that the server is less likely to detect you are both on the same network.