Methods of a first communication device and of a server are disclosed, for enabling inbound Internet protocol (IP) traffic to the first communication device. The server is associated with an operator network and with a wake-up server identity. The first communication device has an operator specific device identity related to the operator network and is subject to network address translation (NAT). A wake-up registration request is transmitted by the first communication device to the server and the server provides a wake-up identifier to the first communication device for triggering a wake-up action for enabling the inbound IP traffic. The wake-up identifier comprises at least a first part indicative of a wake-up device identity and a second part indicative of the wake-up server identity.