I need to fix my MTU to connect to XBoxlive this is the first time this has happened ive had XBL it for a year?

it say : This test confirms that your network has a sufficient Maximum Transmission Unit (MTU).MTU is a setting on your router or gateway that can effect network .Xbox Live requires a minimum MTU setting of 1364. If your console does not p this test, you will not be able to sign into Xbox Live.