A method and an access unit for accessing an industrial communication network are provided. An access unit has first ports connected to the communication network and at least one second port. The access unit is configured to pass data traffic between nodes of the communication network through the access unit in a first operational state of the access unit. The access unit is configured to pass data traffic to a test node via the at least one second port and/or allow test data to be injected into the communication network via the at least one second port in a second operational state of the access unit.