Plutonium

1. Check for Server-Side NAT Solutions
   NAT Traversal Techniques: Some dedicated servers and gaming platforms implement NAT traversal techniques. Verify if the dedicated server software or hosting service provides NAT traversal support or configuration options.
2. Utilize a VPN or Tunnel Service
   VPN Tunnel: Use a VPN service with a public IP to create a tunnel between the clients and the dedicated server. Both the clients and the server can connect through this VPN, bypassing CGNAT restrictions.
   VPN for Game Server: If the dedicated server is hosted on a VPS or cloud service, setting up a VPN on that server and having clients connect via the VPN can help.
3. Public IP from Hosting Provider
   Request Public IP: If possible, ask the server hosting provider if they can offer a public IP address or a way to bypass CGNAT for the dedicated server.
4. Use a Proxy or Relay Server
   Proxy Solutions: Implement a proxy or relay server that clients can connect to, which then forwards the connection to the dedicated server. This can help in scenarios where direct connectivity is restricted due to CGNAT.
5. Configure Firewall and Port Forwarding
   Server Configuration: Ensure that the server's firewall is configured to allow traffic through the necessary ports. Even with CGNAT, properly configuring the firewall can sometimes help in managing connection issues.
6. Consult Hosting Provider for Solutions
   Technical Support: Contact the server hosting provider’s technical support team for advice. They may have specific solutions for dealing with CGNAT and ensuring that clients can connect reliably.
7. Test Different Network Configurations
   Alternate Networks: Test the connection from different networks, if possible. This can help determine if the issue is specific to certain network configurations or if it's a broader issue with CGNAT.

Since youve done most of these here im betting using a vpn will do the trick.

Basically it fools the game into thinking you dont have cg-nat because the vpn tunnel automatically finds the route for you.

indeed. thre only thing i can think of then is cg-nat. i have a open NAT by default in most games and when i hopped on bo2 it was a moderate nat, so your home NAT very well might be strict. if that is the case that is exactly what the issue is. the game is having problems traversing your network and finding its destination.
cg-nat works well for everyday tasks on internet but for games and p2p applications it is a living hell/nightmare

ahhh. that might be why my friend. did your buddy also torrent it?
i understand it sucks paying for the game full price but sometimes it is needed. i suggest adding it to your steam wishlist and waiting for it to go on sale.

You got the full BO2 game from Plutonium? I think you mean the client. Search for BO2 on Steam and buy it. If it's already purchased on Steam, verify the integrity of the game files. Open Steam and go to your library. Right-click on the game—in this case, "Black Ops 2 - Zombies"—then go to Properties -> Installed Files -> Verify Integrity of Game Files.

hrmm. the only thing i can think of is a file is fucked up or something. where did you get your bo2? on steam or elsewwhere? id re-download and see if that worked. also make sure everything possible is up to date. and you say you both have this problem? i would ask your friend about his network setup and see if there could be any factors plaguing you both. (i.e.) firewalls etc, also is your isp using cg-nat? that could pose a problem possibly.. im sorry i couldnt give you the answer you probably wanted, but i still hope this helps you a little.