Embodiments herein relate to a method performed by a first network node (13) for enabling communication between a first wireless device (10) of a first core network in a communication network with a second wireless device (11) of a second core network in the communication network (1). The first network node (13) supports a first set of functionalities out of a total set of functionalities in the first core network of the communication network, which first set of functionalities belongs to a first network slice of the first core network, and is separated from another set of functionalities out of the total set of functionalities in the first core network. The first network node (13) initiates a request transmission, to a receiving network node (17), for communicating with the second wireless device, which request transmission comprises a first network slice identity, first network slice ID, of the first network slice identifying the supported first set of functionalities.