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.
The setting allows you to customize the Teredo client port
The range is 0 to 65535. Default (recommended) is 0 which is to let the local system pick the port.