This policy setting allows you to select the UDP port the Teredo client will use to send packets. If you leave the default of 0 the operating system will select a port (recommended). If you select a UDP port that is already in use by a system the Teredo client will fail to initialize. If you enable this policy setting you can customize a UDP port for the Teredo client. If you disable or do not configure this policy setting the local host setting is used.