What To Do When Your Router Runs Out Of Ethernet Ports

Many cheap routers these days only include 4 Ethernet ports for wired networking, but even if your router includes 8 ports or more, you may encounter the problem of running out of ethernet ports—especially if you use lots of today’s cool networked devices, like voice-over-IP, TiVo, and streaming radio players.

Do You Need To Buy A New Router Because You’re Out Of Ethernet Ports?

If you just want to connect two computers to the internet then you will not need this tutorial, but if you want to go overboard then read on. It seems like the simplest solution when you run out of ethernet ports is to buy a new router. But there’s a problem with that solution—you can only get routers with so many ports. I’ve never seen a router with more than 10 ports, and I doubt they make any home routers with more than 16 ports. What are you going to do if you need more ports than that?
Maybe you think you’ll never need that many ports, but even so, are you willing to risk wasting money on a partial solution when there might be a  way to avoid ever again running out of ethernet ports?

How A Switch Can Help

There is a special piece of networking equipment which can add 8, 16, 32, or even 96 ports to your router. (And you can add several or even daisy-chain them, giving you up to about 10,000 ports with an advanced router.) The device is called a switch.
A switch is a device which “switches” connections between two computers on the same network, similar to the way an old-style manual telephone switchboard operator would switch connections between two telephones so my grandmother could call my grandfather. Of course, the switch is much faster than any person.
Your router actually has a switch built in—that’s what lets two computers or devices on your home network talk to each other without sending any information through the Internet.
The neat thing about switches is that they can be daisy-chained—that’s slang for connecting devices in series. So you can connect a 16-port switch to the 4-port switch in your router and then connect a 8-port switch to the 16-port switch, and so on. In fact, this is exactly how many large organizations manage their networks.

How To Select A Switch

It’s important that you buy a switch, not another router. First it’s important for price—routers are more expensive than switches. That’s because a router includes a switch but also includes more expensive parts that let you configure the router.
It’s important also to buy a switch because some routers can’t be used at pure switches. You can still use them to add ports to your network, but it takes more time to set up and can become quite a headache.
Most switches for home use come in 8-port versions, although 16-port versions are also available.  You can buy another one later, so you only need to buy now whatever fixes your current out of ethernet ports problem.  Be sure you buy a switch that matches your network speed—100 megabits per second (Mbps, also called 100Base-T) or gigabit (which is 1,000 megabits per second).

What Else You Need To Buy

The only other thing you need besides a switch is another ethernet cord. If you use gigabit ethernet, you need a CAT–5E or CAT–6 cable. If you use 100 Mpbs ethernet, you can use CAT–5, CAT–5E, or CAT–6 cable. Of course, make sure the cable is long enough to go from your router to your switch.
Also keep in mind that a switch requires power, so you need space on your power strip to put the switch’s power adapter.

How To Connect A Switch To A Router

Take the ethernet cord you acquired to connect the two devices and plug one end of it into one of your router’s regular device ports—just as if it were going to a computer. Then plug the other end into your switch’s uplink port.
The uplink port on the switch is usually all the ways off to the right side and is offset slightly from the rest of the ports. It may also be colored differently. If you have any doubts, check the manual—but don’t worry too much about making a mistake. Plugging the ethernet cord into the wrong port won’t fry standard equipment—it just won’t work until you plug it in correctly.
After the cord is plugged in, plug in the power cord of your switch. The power on light should come on (the other lights may flash briefly) and then the “ready” light on the uplink port light should glow. The transfer light may blink occasionally.
Now you can connect any of your computers to the switch using you usual ethernet cords. Just plug one end of the cord into the computer and the other end into the switch. (If the computers don’t automatically connect in a few seconds, just reboot them to force them to request a new IP address.)

How It All Works

Let’s say you have a computer connected to a switch, and the switch is connected to your router. When the computer wants to download a page from the Internet, it knows that its “gateway” is your router, so it creates a IP packet addressed to the website and puts it inside another IP packet addressed to the router, then it naively sends it out onto the ethernet cable, hoping that it’ll arrive at its destination.
The switch is on the other end of that ethernet cable, and it sees the IP address of the router in that outer packet. Switches are dumb, so they don’t look for that inner packet. The switch keeps a table in its tiny memory of which IP addresses it’s seen in the last 5 minutes. Since the router sends a special packet to the switch every minute with its IP address, the router knows to which port the router is connected, so it sends the packet there.
The router receives the packet and opens it up, finding the second packet addressed to the Internet. The router then creates a new packet addressed to its gateway—your modem—and puts the original request for the webpage inside that new packet. It sends the packet to the modem and puts a note about it in its table of open requests.
When the website responds, it sends the webpage back to the modem and the modem sends it to the router. The router looks at its table of open requests and notices that the original request came from your computer’s IP address. It looks at its own table of IP addresses and notices that all of the traffic from your computer’s IP address comes from the port to which the switch is connected, so it sends the webpage there.
Your switch gets the webpage addressed to your IP address and checks its table of IP addresses again and notices that all of the traffic for your IP address comes a particular port, so it sends the webpage there.
Your computer gets the webpage, figures out which application requested it, and displays it in your Web browser.

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