1. find out who made your router (Linksys, D-link, etc)
2. find the manufacturer's website and go to it
3. find the support section and look for firmware updates
4. download the updated firmware
5. go to your router admin panel, usually
http://192.168.0.1/
6. login and find the firmware update section, for D-link router's its in the tools panel
7. when it asks find the location of the update firmware you just downloaded
8. let it update... the router will reboot itself and you will have to reconfigure anything you had previously setup. You should now have a "Gaming mode" option to use, which can be access (on a d-link router again) in the tools -> miscellanious menu.
If your router does not support it, try emailing your router manufacturer for further support on this issue as it is their problem, not the game's.