A method for processing cells at a user-network interface with automatic identification of virtual circuit identifiers and a testing function is provided. The method includes distinguishing the source of the cell. When the cell is from a first source, the method tests the cell against at least one selected criteria. When at least one test determines the cell is invalid, the cell is marked. When the tests determine that the cell is valid, the method translates a virtual circuit identifier to a default setting and forwards the cell to a queue for further processing.