Site visitor Craig Nienhuis wrote to ask about a networking problem:
Got directed to your website while Googling to fix my network problem.
I have a simple home network with internet access through cable modem. I have one computer, Vonage phone service and my son’s Xbox that all want access to the internet simultaneously. Have had pretty fair luck making all this work until recently.
Now, I find the network connections through my network switch have universally decided that they will allow only one connection to succeed at a time. I can connect any of them to the cable modem directly, or even through the switch one at a time and they work fine, but through the switch only one will connect, excluding whatever else is connected.
I tried a new switch, just to eliminate that, to no effect. Do I actually need a router to make this work, or is something more sinister going on here?
Thanks for your time and ideas.
Craig’s answer is simple — he needs a router.
The key piece of information is that a switch and a router have similar functions from one point of view. From another point of view, the router is a switch with additional functions.
So, what’s a switch, when we’re talking about a network. First, it is not a power switch. It’s a piece of hardware into which we can plug the Ethernet cables from multiple devices so that they can talk to each other — if they each have a separate IP address on the same network.
In other words, a switch is a connection device for multiple Ethernet networking devices. It doesn’t provide any additional functions that make the networking possible. IP addresses are handled by other devices on the network.
A router has three main functions.
First, it’s a bridge between two networks, usually between the Internet Service Provider’s network (and the Internet through the ISP’s network) and one or more of the your home local area network (LAN) ports on the router. The ISP’s network connects to the Wide Area Network (WAN) port on the router.
The second major function is that a router has a built-in DHCP server. That’s a Dynamic Host Configuration Protocol server; in other words, it has a server built into it that will assign IP addresses to devices on the LAN.
Finally, the router’s LAN ports (sometimes just 1, but usually 4 ports) function as a switch. Yes, the same kind of switch. However, this time, you’ve got the DHCP server to assign the IP addresses and the WAN.
By using a switch between his devices and his cable modem, any individual device is able to function, but not more than one at a time. He is "renting" only one IP address from his ISP. The device gets assigned the one IP address that he’s renting, so it’s not available for the another device.
(At one time, the cable companies thought this was the way they wanted to sell services, but most or all of them now limit you to one IP address.)
If his cable operator will rent him additional IP addresses, he can probably pay an extra $5 per month per address for each them (he would need two more, since he wants to connect three devices). Or, he can get a router for as cheap as $30 and save money after that.
A router, on the other hand, gets that one IP address from the ISP and assigns it to its WAN port. Then, all the devices on the LAN ports are assigned IP addresses on the local area network, usually in the range of 192.168.0.2 through 192.168.0.254.
By connecting the WAN port of the router to his cable modem, and connecting his computer and the other devices to the LAN ports of the router, Craig can have all of them operational at the same time.