successful authentication (peap and TTLS), but internet access that for 5 seconds

Hello everyone, I have a problem with my freeradius server (or maybe switch), the problem is that : I connected a customer on a switch port (Cisco 2940) configured 802.1X Authentication is successful, but I have access to the internet that for 5 seconds and after nothing. I wonder if there is no configuration to avoid this kind of problem. Best regards S.Nick