netgear n150 router dgn1000.I have MW3 but can only play SP and when i got in touch with Activision Support they said it was to do with firewalls and my router not letting the ports through.I dont understand any of it.My port for my router is 192.168.0.1
That's your networks IP address, not the port number. Hold on I'll do some research.
A quick google revealed this:
1) Changed to lcc (as per netgear above)
2) Turn off firewall - Wan ping blocking
3) Turn off UPNp in system settings
I'm not familiar with that router, so I can't give you specific directions.