Wird wohl doch an einem Port liegen der nicht freigegeben worden ist,denke ich.Die Ports müssen natürlich überall freigegeben werden-sprich Router.Firewall,Sicherheitssoftware.
Die Steam Faq dazu:
Q: What ports is needed to host RACE on the internet?
A: TCP+UDP 48942 – 48957 and UDP 26900-26907
Q: I am on a firewall protected LAN network and want to a RACE server for other users of the same LAN network, what ports do I need to open?
A: TCP+UDP 48942 - 48957 and UDP 48958-48973
Q: Why does nothing happen when I click join after having selected a server from the server list?
A: If you click to choose a server and then click join and nothing happens it is more than likely that the server you are trying to join has not been set up with incorrect or missing port forwarding, it is not likely that the problem is related to your internet connection or hardware