SOPHOS NETWORK CLIENT AUTHENTICATION

Hello

Our client wants to limit access to his network, We installed and configured Sophos XGS2300 with web authentication, and the network has 3 VLANs . the challenge is that each time users roam out of the network, it requires them to sign in again when they need to connect. How do we make it a one-time login for already-authenticated users. we tried to use mac binding and clientless user but we realized that mac addresses for mobiles, especially iPhones, are random, making it difficult