- Ghost Unknown
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- Exalted Legendary Member
Firstly, make sure you have updated the game to the latest version using the manual updater in the game's directory.
Secondly, you will need to do some port forwarding. Find your router on this list and then follow the instructions.
If you've changed the incoming/outgoing ports for Halo in your settings menu, you'll need to reflect that change when you're configuring your ports. Make sure you also modify the port settings of any software firewalls you may have, or set them to disable when you launch Halo.