A method and arrangment for enrolling a joining peer (202) to a P2P (peer-to-peer) to the P2P network receives (2:2) a connect request sent from the joining peer, and obtains (2:4-2:7) an enrollment recommendation for the joining peer at least based on a stored current topology (208) of the P2P network. The enrollment a server then sends (2:9) attach information to the joining peer according to the enrollment recommendation. The attach information indicates where the joining peer shall connect to the P2P network. The enrollment server also updates (2:13) and stored toplogy of the P2P network when the joining peer has connected to the P2P network.