Hi Wasfi,
I suspect that the proxy does this based on the IP address of the client.
Accordingly, the LEASE time in DHCP should be set to one week, or DHCP should always give all clients the same IP address.
Why do I think it is done this way? A proxy shows in its user statistics the number of Client IP addresses and not the number of users - even if it does an authentication of all users. I know of cases where Citrix servers are used. There are about 20 users on one terminal server and the proxy shows only one user aka one IP.
Best regards,
Klaus