It seems like your NAS sends accounting Stop for the previous session (nas-port is different) after receiving the response of of the accounting Start (for the new session)... this would show your NAS ask the radius to notice a disconnection hit has decided... I don't know how netscreen works, but neither Access-Accept nor Accouting request have any Framed-IP-Address or anything ppp related... looks strange to me. This can mean that whereas established the vpn connection doesn't work (you can easily test this) or netscreen is managing ip allocation by its ow, and so you should take a look at its config to see if it's able to offer different IP addresses for one login at the same time (If it tries to give every body the same address, no doubt it won't work unless it disconnects the previous session)... Or you can ask freeradius to handle ip allocation, depending on your config