Final answer:
Connect the Cat5e cable to the WAN port on the gateway during an ETTS installation for internet connectivity.
Step-by-step explanation:
During an ETTS (Ethernet to the Subscriber) installation, you should connect the Cat5e cable to the WAN (Wide Area Network) port on the gateway. The WAN port is specifically designed to connect the network to the internet or an external network. It's important to use the correct port to ensure your network functions correctly and to provide internet access to all connected devices.