Assuming this is an actual "modem" or "in bridge mode", it's highly unlikely your ISP offers up multiple public IP addresses, unless you have a business connection at home, so that sounds pretty normal to me.
You should always have your modem go into your router anyhow though so that you get a firewall and NAT to stop the whole world from seeing every open service on every device you plug in. I surely wouldn't want my TV on the open Internet, who knows what will show up on your screen...
You should always have your modem go into your router anyhow though so that you get a firewall and NAT to stop the whole world from seeing every open service on every device you plug in. I surely wouldn't want my TV on the open Internet, who knows what will show up on your screen...