Also as an update to what has been attempted, I've now changed my ACL entries to have one Xbox be allowed 3074, the next 3075, the final 3076, then 2 rules for all of them to be allowed to grab 53-3073 and 3077-65535, as it seems from another forum that this was Activision's suggestion. Still no dice.
You cant do that.. Xboxs try 3074, then a Random Port (40k+) for Teredo, you MUST allow Xboxes to grab ANY port they want, the ONLY one you can deny is 3074, nothing else.
You can not force an Xbox you use certain ports by restricting what UPNP will allow, the Xbox will just give up since UPNP doesn't tell it "you can only use these", the Xbox ask UPNP, "can i use this", UPNP say nope, Xbox ask then "can I use this", UPNP says nope, Xbox gives up.
The ONLY UPNP rule you should have is.
deny 3074 192.168.1.0/24 3074 <<---- Replace 192.168.1.0/24 with you LAN SubnetThis forces the Xboxes to pick a different port for "Teredo", this also allows all games on all Xboxes to UPNP themselves another port if they need it.
As far as UPNP goes, every Xbox MUST be allowed to use every port except 3074.
In my setup, I have no Xbox Dedicated Inbound or Outbound NAT Rules, the only thing Xbox Related is a deny ACL for 3074.
For Outbound NAT my whole LAN has Static Port, making a separate rule is not very helpful, and forcing random ports for LAN devices hurts worse then it helps anyways, not that it hurts much, point is it offers practically 0 benifit.
I have UPNP only Blocking the use of 3074 "deny 3074 10.0.1.0/24 3074".
Then for "NAT Loopback" or "NAT Reflection" I have
Goto System -> Advanced -> Firewall & NAT
NAT Reflection mode for port forwards: Pure NAT
Enable automatic outbound NAT for Reflection: Check/Enabled
That is it, Xboxes have full open NAT, any Games can UPNP more ports if they need, and they can talk to each other via the WAN IP.