A method and device for routing data packets of a wireless terminal device in a communication network. When Open system Authentication is used, the system operates similarly as the current Nokia Operator Wireless LAN system, in which the terminal device and the access controller are the parties involved in the authentication. The access controller relays information relating to the authentication between the terminal device and an authenticating server, and it is capable of updating independently the list of users it maintains. When authentication according IEEE 802.1X authentication, the access point operates according to the IEEE 802.1X standard, serving as the authenticating party and relaying information relating to the authentication between the terminal device and the authentication server. In addition, the list maintained by the access controller is updated after a successful authentication, for example by the access point or the authenticating server.