Routing - what is a WAN port
The term WAN port can be misleading when we talk about devices capable of connecting to the Internet. The term WAN port is often used loosely by vendors to refer to specific capabilities of a particular port on a device.
In order to connect a router to the internet, you don't need a port specifically labeled as a WAN port. Nothing prevents you from connecting your Layer 3 switch or your router to the ISP and performing routing between your WAN connection and your internal VLANs and subnets.
Some cheaper vendors that offer lower end edge routers that may support xDSL or cable connectivity, or even some wireless routers, may have a port labeled as the “WAN” port. This is useful for those not as well-versed in networking. This is just a routed port, nothing more.
Higher end routers will not use this terminology, since you can configure any port you choose to be connected to the ISPI and any other port to be connected to the rest of your network.