Found a solution on Halo CE Co-op "connection interrupted"

[P-Slayer]

Both players launch the SAME MISSION on single player first with the SAME DIFFICULTY and SAME SKULLS turned on. After that, both players exit the single player mission and join co-op. Make sure you wait for a bit before that player joins otherwise there will be a message saying that you can't join a game. Take turns hosting the game if possible. Restart your PC as a last resort. It worked for us so hopefully it should for work all of you guys. I do not know why but that is the way to fix the problem. Let me know if it works for you guys.

[Jammin Joey (Fiancé)]

I finally found something that worked!
I have gone through 100 threads and tried them all but these things finally made it work for me and my coop partner!
We were playing on the SAME router side by side and it would still kick us at random saying there was a connection interruption.
I got the idea to change my online region to the 2 closest regions to us. We live on the west side of the US so I believe I picked US WEST and another Central (You need to have 2 regions selected for MCC).
In addition to this, we also noticed that you have to run Halo 2 at only 60 FPS. The 60 FPS & changing regions were the fix.
After we both changed this we have never been kicked again and were able to Complete Halo 2 Coop Legendary. :)

P.S. We had moments where we completed a mission then as we were loading the next level the host would see the next level loading and the coop partner would see the current mission we just completed loading. When this happens the host will get the completed mission but not the coop partner. We would have to do this mission again but switch making my partner the host (They also had to have 60 FPS and region switch of course) I have no idea on this one but at least we are able to finish a mission without interruption.

[Define Brackish Water]

Ursprünglich geschrieben von Jammin Joey:

I finally found something that worked!
I have gone through 100 threads and tried them all but this one finally worked for me and my coop partner!
We were playing on the SAME router side by side and it would still kick us at random saying there was a connection interruption.
I got the idea to change my online region to the 2 closest regions to us. We live on the west side of the US so I believe I picked US WEST and another Central (You need to have 2 regions selected for MCC)
After I changed this we have never been kicked again and were able to Complete Halo 2 Coop Legendary

That's awesome to hear.

If you want to formally badger 343i about the problem in the most helpful way possible, you can send it in as a bug report here:
https://support.halowaypoint.com/hc/en-us/articles/360036218972-How-to-Submit-a-Ticket
I'm a bit worried about how much work 343i is putting into MCC now, but it's worth a shot. I've known about people having issues in multiplayer when playing in the same house (using the same router) over XBL for years so this might be a helpful piece of the puzzle.

[I AM HIM]

343 is trash at everything they do

[Jammin Joey (Fiancé)]

Ursprünglich geschrieben von Define Brackish Water:

Ursprünglich geschrieben von Jammin Joey:

I finally found something that worked!
I have gone through 100 threads and tried them all but this one finally worked for me and my coop partner!
We were playing on the SAME router side by side and it would still kick us at random saying there was a connection interruption.
I got the idea to change my online region to the 2 closest regions to us. We live on the west side of the US so I believe I picked US WEST and another Central (You need to have 2 regions selected for MCC)
After I changed this we have never been kicked again and were able to Complete Halo 2 Coop Legendary

That's awesome to hear.

If you want to formally badger 343i about the problem in the most helpful way possible, you can send it in as a bug report here:
https://support.halowaypoint.com/hc/en-us/articles/360036218972-How-to-Submit-a-Ticket
I'm a bit worried about how much work 343i is putting into MCC now, but it's worth a shot. I've known about people having issues in multiplayer when playing in the same house (using the same router) over XBL for years so this might be a helpful piece of the puzzle.

Good idea! I went ahead and sent something their way! I am just grateful that we truly found a fix to complete a mission without getting booted! Good job Halo 2 community!