Adding a TV to home network -- do I need a router?
March 6, 2010 7:53 PM   Subscribe

Simple (I think) question about cable modem + home network: Would like to add TV -- do I need a router, or just a different modem?

I just bought a TV that, if you hook it up to the internet via its ethernet port, can access Youtube, Picasaweb, and a few other things.

Here is my current setup:

Cable Modem -> Apple Airport Express (model A1264)

I tried wiring it like this

Cable Modem -> TV

and it worked just fine. But the cable modem only has one ethernet port, and I would like to be able to keep my TV and my Airport Express plugged in at the same time. Do they make cable modems with more than one ethernet port? Or do I need to get a router, and wire it:

Cable Modem -> Router -> Airport and TV

I'd rather not get a router -- just one more piece of electronics cluttering up my small, borrowed living space -- but if I need one, what would be a good, inexpensive one to get?

Any guidance appreciated.
posted by Alaska Jack to Computers & Internet (15 answers total) 1 user marked this as a favorite
It depends on the make/model of your cable modem, and your ISP - some modems are just modems that pass the ISP's assigned address to the local network; others are routers that assign addresses to the local network & route those through to the ISP.

If yours is the latter, a simple hub or switch would suffice. Give us the modem & ISP details & we can tell you more.
posted by Pinback at 8:18 PM on March 6, 2010

Need to know more about your cable modem. But it probably does NAT, which means you can plug multiple devices in; you can just get an ethernet hub or switch, no need for a router. [On preview: exactly what Pinback said.]

They do make cable modems with embedded hubs/switches, if you want one fewer blinky box. Heck, they make ones with embedded wifi access points as well (for example, first one that came up on google)
posted by hattifattener at 8:21 PM on March 6, 2010

You probably don't need a router, just a switch.
posted by flabdablet at 8:22 PM on March 6, 2010 [1 favorite]

You don't need to get a router, although it would help in this situation.

There are two options, as I see it. Whenever I design a network layout, I try to keep as few steps between the client computers and the internet feed as possible. It simplifies things generally, and makes diagnosing network problems easier if they arise. So, with that in mind;

An ethernet switch would be a simple, albeit somewhat crude, solution. An ethernet switch takes an ethernet connection from somewhere else (e.g. your cable modem) and gives you several more ports to work with. Typically they come with four ports, though you can get more if need be. If you got one, your network would look like this:

Cable Modem —> Ethernet Switch

at which point one port is connected to your AirPort Express, and another to your TV.

This is the cheapest solution, and if you don't see yourself adding any more wired devices to your network, the easiest. You can just throw it into your existing setup, and all you need is a few more ethernet cables. Switches, assuming you're in the U.S., cost between $10-$20 for 4-5 ports.

The other solution is to get a router with a cable modem included. This would have several ports (again, typically the number hovers around four) and mean one less device. You'd need to configure it and so on, but this isn't too difficult. These appear to cost around $50 (so sayeth Amazon). Then things would go straight from the router to the AirPort Express and the TV.

The switch is probably the best idea, all things considered. Cheaper and pretty painless to add into the mix.
posted by jaffacakerhubarb at 8:26 PM on March 6, 2010

Get a cheap DLink switch or something along those lines.
posted by signalnine at 9:44 PM on March 6, 2010

Thanks for all the great info so far! I really appreciate it.

The cable modem is an RCA model DCM425, if that helps. Like the picture shows, it only has one ethernet port, but I suppose I could just ask my ISP (GCI) if they have any models with additional ports?

Otherwise, it sounds like a switch would probably take care of my needs. I just didn't want to buy one and add it to the setup if I didn't need to.

Thank you again, everyone!
posted by Alaska Jack at 9:46 PM on March 6, 2010

PDF page 25 (marked 23) of the manual available via the page you linked recommends using an Ethernet hub to connect multiple devices to that modem. Unless you're doing something clever with network monitoring, any configuration that calls for a hub will work at least as well with a switch.

Switches allow any pair of connected devices to converse with each other without needing to wait for other, uninvolved devices to get out of their way; hubs don't. For example, if you had two computers and your TV and the cable modem all plugged into a switch, the computers could be transferring files between themselves at full network speed without affecting the Internet bandwidth available to the TV even slightly; doing the same thing with a hub, you might see a bit of video jerkiness.

A typical, generic 5 or 8 port switch will sit very neatly under that modem, and provided you use the shortest available patch cables to link everything together, could well end up looking neater than a bigger modem with more ports inbuilt.
posted by flabdablet at 10:52 PM on March 6, 2010

OK … looking at the manual on that page, it appears that it's just a modem - that is, all it does is hand on the address(es) sent to it by your ISP to the connected devices.

It looks like your ISP will hand out multiple addresses to a single modem connection - see the "Can I connect more than one computer to my Cable Modem?" entry in their FAQ - but that entry is from 2006, so YMMV. Best contact them and ask. If they still do, a hub or switch will work; if they don't, you'll need a router.

It's not often I'd recommend a hub over a switch, but I will in this case for two particular reasons. Firstly, you can buy small unpowered 2 port hubs, which are basically a double-adaptor dongle. They take up about as much space as a box of matches & plug straight into the back of the modem - no blinkenlights, power supply, etc. Secondly, if you're only connecting 2 devices and just occasionally browsing YouTube, PicasaWeb, etc from the TV, then you'll avoid the majority of collision problems etc inherent with hubs.

(Hubs are dumb devices; they basically connect all the wires together and let the devices sort out the details. The upshots of which are a) all devices must communicate at the speed of the slowest, and b) 2 devices may try and send at the same time, causing a collision which slows things down a bit as the devices then wait for a short random time before trying again.

On the other hand, switches are slightly intelligent devices; they mediate the connections to largely avoid those problems. However, they require some smarts to do this, & that means a bigger device that requires a power supply.)

(On preview, largely what flabdablet says, only I said it longer ;-)
posted by Pinback at 10:54 PM on March 6, 2010

Which is not to say that hubs are totally unpowered - the little 2-port hubs I use (they're labelled 'Targus', but I know they're cheap knock-offs) are parasitically powered off the ethernet (not PoE). I can't find any of this type on-line anymore, so you might have to buy a powered one. In which case, you may as well buy a switch :-/
posted by Pinback at 11:54 PM on March 6, 2010

If you think you'll be getting any wifi devices (laptop, smartphone, ipad, etc.), you may as well get a wireless router. Just disable the wifi until you need it. They aren't much, and it's cheaper than buying it on top of the switch in a year.
posted by backwards guitar at 4:50 AM on March 7, 2010

OK, so what I think I've gathered is that a good solution would be to order this

TRENDnet 5-Port Ethernet Switch (5 x 10/100Mbps Auto-MDIX RJ-45 Ports)

(about 12 bucks from Amazon)

and do this

Cable Modem -> Switch -> Airport Express
................................ -> TV

If I get the thumbs up here I'll go ahead and order it, and report back with the results!
posted by Alaska Jack at 1:23 PM on March 7, 2010

That's what I'd do. It's about the simplest thing that could possibly work, and it will cause you no configuration difficulties.

If you want to do something more complicated later (like hooking up computers in a wired network, for which job you certainly do want a router between wired LAN and Internet) then a switch is a handy thing to have around. You can use it to give a router more ports, or to set up a cluster of PCs and printers all connected back to the router via one cable.

Even if it never gets used for anything except this job, you're only out twelve bucks.
posted by flabdablet at 4:21 PM on March 7, 2010


It worked! Although it didn't at first, I think because the switch comes with VERY skimpy instructions, and didn't clearly specify that the cables have to be plugged in to specific ports. At least, I think that was the problem, because I managed to get the setup working after trying a few different combinations of ports.

Now I just need to figure out how to make all the junk (dvr, vcr, cable modem, switch, dvd player, tv and a rat's nest of cables) look halfway decent.

Thanks to everyone for their help!

- AJ
posted by Alaska Jack at 3:34 PM on March 25, 2010

Sounds like you ended up with a switch that doesn't do MDI/MDIX auto-configuration. I had no idea people were still selling those.

Glad you got a result.
posted by flabdablet at 8:36 PM on March 25, 2010

The key to getting a rat's nest to look decent is using the shortest possible patch cables. Retractable ones can help, too.
posted by flabdablet at 8:39 PM on March 25, 2010

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