After trying to connect to xboxlive yesterday, it said that my computers MTU settings were to low for the Xbox requirement.
So i check my computer and it was at 1500, and the xbox requirement is 1364.

I have no clue what is wrong with it, i've changed that settings millions of times.
I would just like to know whats wrong, has anyone else had this problem?

If I remember correctly the optimal MTU settings for Xbox Live are between 1364 and 1492.

oh really? that may help

Yeah, try lowering it to 1365 and see if it works. Are you port forwarding to the Xbox as well? Or DMZ?

how can i tell that?
im not big into this technology stuff.

Then you are not. You would know if you were, since you have to manually port forward. Did changing the MTU have any effect?

No i changed it to 1365, 1400, 1492.. nothing..

The MTU should never be changed. Most people use the default setting of 1500. I believe DSL operates at a slightly lower setting.. 1492. However it doesn't matter, I wouldn't recommend changing the MTU setting unless your ISP states to do so.

A low MTU can be caused by a communication problem.

Reboot your Router and Modem.
If you have your XBOX connected via Wifi (802.11) then ensure it has a strong signal to the router.
Ensure that all required ports are forwarded to the XBOX 360's local IP address.

• Port 88 (UDP)
  
• Port 3074 (UDP and TCP)
  
• Port 53 (UDP and TCP)
  
• Port 80 (TCP)

I recommend enabling UPnP.

If it still fails to connect then you may need to contact your ISP to service your connection.

Edit: BTW XBOX 360 needs a MTU of at least 1364. There is no cap, however 1500 is the maximum of Ethernet.