This is a how-to guide to release your IPTV port on Asus RT-N18U and use it as a normal LAN port

1. You are subscribed to Unifi Home
2. You do not use IPTV, crappy programs anyway!
3. You do not want to add another switch to your Asus router
4. Your LAN port 4 on your Asus router is fixed for IPTV. The router interface does not give you an option to modify it.

Procedure:
1. Login into your Asus router home page on your browser
2. On the left pane, select LAN
3. On the tabs, select IPTV
4. Drop down the box that says Unifi-Home, and change it to Unifi-Business

That's it. You can now use LAN 4 on your Asus Router as a normal LAN port.

Hope someone benefits.