Good day to you. Thank you for writing to Xbox Live Technical Support. I do apologize for the inconvenience.
When you try to join a party session or when others join a party session on Xbox Live, you may receive the following error message: You aren't able to join this party because we're having network problems. Sorry about that. Currently, MS is researching this issue. Hopefully would be developing an update which would be available in the future.
Though NAT poses a great factor in this. When you have multiple devices on your home network sharing one Internet connection, the devices typically perform this sharing through Network Address Translation (NAT). It doesnât have to anything to do with security. A router performing âopenâ NAT is no less secure than a router performing âstrictâ NAT. The classification system boils down to something called a port assignment policy. Open NAT means that either the port assignment policy is minimal or the router has a fully compliant version of UPnP (Universal Plug and Play) enabled by default thus allowing players to freely connect to you. Moderate NAT means that the port assignment policy is minimal, but there is address or port filtering taking place. Strict NAT means the port assignment policy is aggressive making game hosting a nearly impossible. With most NAT-type routers, you can connect to the Xbox Live service. However, if you, or other gamers you play, use an aggressive NAT-type router, you may experience some of the following symptoms: You can play with one person on your friends list but not another; You cannot connect with a particular host in game sessions. You cannot hear voice during game sessions, even when you can play without interruption.
Some routers donât have the option to lower down the NAT setting. Workaround for this is opening ports for the Xbox to use: UDP 88 and UDP 3074 and TCP 3074 respectively. This is done by accessing the routerâs GUI or interface.
If you have more questions or inquiries, feel free to write back or call us at 1-800-469-9269. We are open from 9am to 12mn CST. To expedite service please provide service request number SRX1015331954 when you call.
Sincerely,
Amber
Xbox Live Technical Support
This is the respnse I got From MS. I haven't tried it yet, but it sounds like it might work.