An approach is proposed that contemplates system and method to configure firewall rules of a VPN gateway of a protected network so that users of devices in the protected network can access Internet securely via a captive network. First, the proposed approach enables the VPN gateway to probe the captive network with an HTTP request to discover a captive portal of the captive network. After the captive portal is discovered, one or more firewall rules of the VPN gateway are added so that network traffic from the devices in the protected network are redirected to the captive portal for authentication. Once the users are authenticated and a VPN tunnel is established between the VPN gateway and a remote VPN tunnel terminal, the firewall rules previously added are removed from the VPN gateway and all network traffic from the devices in the protected network are routed over the VPN tunnel.