Your router routes. It also assigns IP addresses to devices. So no, you can’t just connect a switch to a modem and be Online. It may be possible if your ISP gave you multiple IP addresses and you set them static to your devices, but you also do not want your private devices directly on public Internet.

In most residential service, the ISP configured the modem to provide a single public IP address. Besides serving as the point of connection to the modem, a router serves a few critical purposes:

1. Provides a firewall to protect your network from malicious intrusion attempt from the Internet

2. Provides the needed DNS and DHCP services to devices on your network that allows them to have an IP address and the ability to find external sites

3. Manages the IP address translation and routing required to allow all of your network devices use a single public IP address

If you connect your modem directly to a switch that connects to your network, the first device that requests an IP address will get the single available IP address and none of the others will get a usable IP address and as a result, will not be able to access the Internet. They also will be lacking the services provided by a router as listed above.

Please get a router!

As others have said, your cable modem may have a router already built into it. Usually, these also include WiFi. So, if your cable modem has WiFi, it already has a router built-in. If it doesn’t, you need a router. Most people use a WiFi router or a mesh setup with multiple access points is common these days.

However, you definitely do NOT need a smart managed switch - especially if you don’t understand what a router does. If you need a switch, just buy a cheap unmanaged giga switch.

No, because a switch can’t route traffic from one point to another. Specifically, it can’t do NAT. Without NAT you can only have 1 device connected to the internet.

You need something to manage your clients on that network. If your modem can do that, good, you may not need a router. If the modem can’t or it is not setup-ed and you can’t access it, then you most likely would need one.

A modem modulates/demodulates. A router routes

Most modems these days are combined with a router. So yeah you can use the routing capabilities and plug into a smart/dumb switch and it will work

Unless you have purchased a VERY large block of external routable IPs, no. Your devices would have no idea how to get out to the rest of the world. Also, I know some switches can also route, but then they are essentially routers.

It depends on your cable modem. If it has routing capabilities (can provide internal IP addresses and can pass data… or route it… between the single external IP and those internal IP addresses of the devices on your home network) then technically you have a router and don’t need an additional device.

Look for options in your cable mode like “DHCP server” and “firewall” to indicate it has routing functionality.

thanks for all the replies. very helpful

Yes you need one. And the world Router is self explanatory.

Technically possible with a layer 3 switch but routing is still required and best done with a purpose built router.