NAT help

I'm having the same problem. I'm using a Huawei E586 on 3 and my NAT type is strict and ive tried allsorts to get this sorted if anyone has over come this problem please let me know as Battlefield 3 aint the same without being able to communicate with my
team mates.

Your logging into the router with the wrong router IP. The IP for your Linksys WRT54GSV1 should be 192.168.1.1. The default username should be blank and password should be set as admin. These of course are settings by default if you have not previously changed
them. You can get in there and then follow the instructions on this site
here. Just push the x on the top right hand side from the little popup that comes up asking if you'd like to pay for the program
and you can view the instructions manually. Let us know if you need further instructions than those that are written in the guide for your router.

Yes. I would try setting your Speedstream 4300 to bridged mode and letting the Linksys handle PPPoE (if necessary) and then try using just UPnP with your Linksys. If you search the web, you'll find a bunch of tutorials on setting the Speedstream to bridges
mode.

Two Xbox on one network shouldn't be a problem. If you have trouble with UPnP or port forwarding, you can always put one or both Xboxen in the DMZ.

Yeah, I called then but they charge a fee, I can't afford to pay for it so I think there is nothing I can do

If I plug it directly it just gives me a strict NAT

If I plug it on my own router it gives me double NAT (sometimes with moderate and sometimes with strict)

I used a method of cleaning the alternate Mac and then going on offline mode and restarting the Xbox, the modem and the router, and when the Xbox restarted, going online again and testing the NAT type, the NAT Opens, but now when I try this it gave me a
"fake NAT", when I start a game it goes to moderate or strict again, I don't know what to do to open the NAT anymore...

You probably need to go back to your provider. Is there no sticker or paperwork with how to get to the admin modem settings? Usually best done with a hardwired pc/laptop until you get all the kinks worked out.

If you look up the make and model online you might also find helpful info.