Problem with "Fragmented IP protocol"

Hi again, As I wrote yesterday, we have an Access Point in one office, connected via OpenVPN to the main office. Freeradius runs on the main office. When trying to authenticate with EAP-TLS it does not works (APs in main office have no problem). With Wireshark I see the error: 13 0.480756 10.6.21.9 10.0.21.10 IPv4 1516 Fragmented IP protocol (proto=UDP 17, off=0, ID=a62d) The packet was fragmented, but seems to reach the server with Freeradius. Can someone help me to solve the problem? Thanks a lot Luca Bertoncello