Maybe you could tell us your routers make & model.

Typical home router has 1 wan ethernet port that hooks to modem for the main internet connection.

And 4 lan ethernet ports, to divide the main connection up up for multiple devices that connect to the www - like 1, 2, 3 or 4 computers & Roku's with ethernet ports.

Mikie, Router is D-Link Wireless N 150 as you described - 1 ethernet port and 4 Lan Ports.
Only 1 of the latter ports is not being used. Can't find anything describing the LAN Ports as being ethernet.
Roku XD is what I want to connect -- this time with a cable to the computer. Wireless connection has been too erratic.

Of those 4 ports, if onle one is used.. You're in good shape.
Those are all ethernet ports. The one main, that has its own color on the back... goes to the modem.

The other 4 are color coded all the same blue in the web Picture & are made specifically for ruku's & computers..

You will need a standard ethernet cable of appropiate length to reach beween one of those empty ethernet ports and your rucu's ethernet port. Pretty simple.. just plug it in on both ends.. Hard part is trying to hide the cable from puppies & cats that like to chew & play tug-a-war.

Here is a link that might be useful: http://prntscr.com/5lvru back of Dlink

Just to clarify your router has one WAN port and four LAN ports. WAN is Wide Area Network (the Internet) and is Local Area Network (the network inside your home). You use the LAN ports to connect to devices on your local network, which would include computers and other Internet enabled devices like the Roku.

Mikie, Thanks for the fast response. Only one of the LAN ports is open -- the rest are being used.
Anyway, I'm relieved to know that all those ports are ethernet. Was under the impression that they
were just standard ports. You've taken a big load off my mind! Just have to buy the ethernet cable
now so my Roku can be back in business.
You're been a great help and saved me more headaches that I can say. No pets to (further) complicate
things. Will get that cable now. Thanks again.

Mike, I appreciate your explaining more about the ports. The diagram you so graciously provided is
different than my hook-ups, but helpful anyway. (Aside from the cable modem connected to the router,
3 ports are being used for my other computers.)

For all practical purposes, home networks today use only two networking technologies - Ethernet (wired) and WiFi (wireless). If you buy a modern router, you're buying one that has Ethernet ports.

The typical hook up is:

Cable or DSL Modem --> Router's WAN Port and the router's LAN (Ethernet) port or WiFi --> Computer and Internet connected devices

For some services the ISP may provide a single box that is both a modem and router. For services like Verizon's FIOS and AT&T's Uverse, that box is called a "gateway" and is a modem/router plus handles the telephone. In either case, the device should have at least one LAN port.

If you run out of LAN ports, you need to add a "switch" to the mix. Think of a switch as being analogous to a power strip for electricity. It just gives you more space to plug things in.

Thanks, Mike, for the additional education. Before I started this post, my search for answers
provided terms like "hub," then "switch," then came the "you might have to change the IP address"
and other such daunting ideas. So glad there are people like you and Mikie to assist and simplify!