Unknown Service Class – SonicWALL

When trying to configure NAT Policies on a SonicWALL, you get this error:

Unknown service class

This is because either:

• You are translating one port to more than one port, or vice versa – You must make a separate NAT Policy for each port you wish to translate; you can only translate one port into one other port.
• You are trying to translate a UDP port into a TCP port, or vice versa.

Creating a NAT Policy in either of the above scenarios causes the Unknown service class error in SonicWALL.