Samsung PN51D490A1DXZA E-Manual page 110

If Your TV Fails to Connect to the Internet
Your TV may not be able to connect to the Internet because your ISP has
permanently registered the MAC address (a unique identifying number) of your PC
or modem, which it then authenticates each time you connect to the Internet as a
way of preventing unauthorized access. As your TV has a different MAC address,
your ISP can not authenticate its MAC address, and your TV can not connect.
To resolve this problem, ask your ISP about the procedures required to connect
devices other than a PC (such as your TV) to the Internet.
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If your Internet service provider requires an ID or password to connect to the
Internet, your TV may not be able to connect to the Internet. If this is the case, you
must enter your ID or password when connecting to the Internet.
The internet connection may fail because of a firewall problem. If this is the case,
contact your Internet service provider.
If you cannot connect to the Internet even after you have followed the procedures
of your Internet service provider, please contact Samsung Electronics at
1-800-SAMSUNG.
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