Symmetric Nat Punchthrough Problem

Hey, I recently updated my engine to 3.0 and found that the networking code changed. So I updated my code to suite this Networking platform. Here is the problem: I tested my code on all machines that used to have a properly working NAT Punchthrough enabled configuration. In every case the facilitator reports a Symmetric Nat and the connection fails. Is there a workaround avaible (port prediction), or anything I should know of? Thanks in advance, Vinpasso