If you are using PPPoE (Point-to-Point Protocol connection through an Ethernet network adapter) you have a special circumstance which may require some experimentation. You can confirm with your ISP if yours is a PPPoE connection, but generally this applies to broadband connections like DSL or cable where you must logon with a password (unlike “always on” broadband connections).
If this applies you you, you should check the box in the TweakMASTER wizard which says “I need a username/password to connect.” This will set your MTU to 1492 which is a good starting point for PPPoE connections. Note that using the standard 1500 MTU recommended for regular broadband connections, will often result in a total loss of connectivity.
PPPoE requires that, on all client computers, you lower the setting for maximum transmission unit (MTU) size to a value no higher than 1492 (the default is 1500). In some cases, a value lower than 1492 may be necessary.
ping -f -l MTU_size default_gateway_IP_address
After you determine the largest MTU size that is supported, manually set the MTU.
PPPoE is described in RFC 2516. Like PPTP, it is used by service providers because it’s much cheaper for them. It lets them connect their old systems directly to DSL redbacks, simplifies billing, etc. But it’s a pain for the user, decreases network bandwidth, and has a list of other problems (like this one with MTU).