Fortigate Proxy

 Explicit Proxy

1. Enabled explicit web proxy, indicating interface listening on.
2. Create Authentication Scheme, choose from Form-based, FSSO, RSSO, NTLM etc.
3. Created Authentication Rule, specify source IP,  link the scheme
4. Create proxy polices: Type: Explicit Web, Server: webproxy 

5. Configure client's browser

Transparent Proxy

1. Create regular firewall policies, Enable http-policy-redirect on firewall policies (CLI only).
2. Create Authentication Scheme and Rule.
3. Create proxy polices: Type: Transparent Web, Server: webproxy