How to open nat on A westell 7500 router for xbox play.?

Hello everyone! I just swtiched between a linksys router to a westell router. When I did, it closed my nat up. This has affected by gameplay severly, as it makes me lag more and doesn't let me connect to alot of my friends. Can you tell me how to open the nat for my xbox 360? And 192.168.1.1 is the ip address for a linksys and I already tried it, it doesn't work. Thanks for any help!