What does the Ignore DF (Don't Fragment) Bit checkbox do?

Some applications can explicitly set the ‘Don’t Fragment’ option in a packet, which tells all security appliances in between to not fragment the packet. This option, when enabled, causes the SonicWall to ignore the option and fragment it anyways. This option is a sub-option of the ‘Enable Fragmented Packet Handling’ option and can only be enabled if it is too.