On-off switch for Ethernet?

I have an Ethernet socket that is on the outside of my shop for connecting a network printer. I am concerned that somebody could bring a laptop and connect to that socket, then he will have access to my network.

So I am looking for a simple on/off switch that will easily disconect this run of cable from the switch.

I couldn’t find anything on the net so I am thinking of joining together two 4-pole switches (i can’t find an 8-pole switch) and make my own switch. Will this work?

Why not just disable that circuit in your router config?

The router has nothing to do with it. I don’t care if they leech Internet, I want to protect my internal network.

It would be possible to disable that specific port if I had a managed switch, but I don’t and besides this process will have to be repeated every day when the shop opens and closes by not tech savvy people.

Another solution would be to pull the cable directly from the switch, but I don’t feel comfortable with them messing with the switch and I fear one day they will pull the wrong cable.

Would it make sense to restrict access to your network by MAC address, instead?

I could do that on the router and restrict access to the internet. It would have no effect on the internal network.

Ah, my mistake. I thought you’d be able to restrict routing of all packets from non-approved addresses.

Not an on/off switch but you can buy cable coupler connectors which join two flyleads and unplug one side when you want to disable that port.

BTW switch has a specific meaning in networking hardware.

Yes and no.

Ethernet is both remarkably resilient, and also rather fragile. Which sounds contradictory. But the problem is this. Ethernet runs at reasonably ridiculous signalling speeds, and the success of high speed Ethernet depends upon the maintenance of the characteristics of the cable within reasonably fine tolerances. The ubiquitous RJ45 plug is already at the ragged end of what can be managed for very high speeds. Just splicing some cable into a generic multi-way switch which does not maintain impedance and avoid cross talk between the pairs could result in a link that suffers from significant problems. That is the fragile part. Because Ethernet does not actually provide any delivery guarantee the protocols that use it need to be resilient to that, and thus even with a very flaky Ethernet connection you can get some semblance of a working network, albeit with significantly degraded performance. That is the resilient bit. You could make a switch and connect it up, test the network with a trivial test, see that the computer thinks there is connectivity, and yet not realise that the overall performance was appalling.

My suggestion is to simply buy a very cheap hub/switch and use it to connect the printer to your internal network. Turning it off will isolate the printer connection. Simple, and given how cheap these things are, probably much cheaper than an hour of your time plus the cost of the parts in making a (probably) flaky switch.

ETA - for 100 Mb/s Ethernet you only need to switch two of the the pairs, the other to are not used. Gigabit uses all four pairs.

Use an additional short patch cable and a straight-through RJ45 coupler to move the point of disconnection outside of the cabinet.

rewiring the socket to unplug from a patch cord on the inside makes sense.

a piece of duct tape or poster or calendar would also work.

Why not use a cheap wired Ethernet router or hub? I’m sure you can find a used one for cheap on Craigslist or PC recycler. Daisy chain it from your current one, only for the line you want to limit. Plug it into a switched outlet or power strip.

Buy one of these and have the A side go to the outside socket, the B side empty. When you want to turn off that particular run, move the switch to B. Easy peasy. :slight_smile:

Not a physical switch (as in an on/off switch you can just toggle), no. If your switch (the thing you plug your ethernet cables into to make your network work) is reasonably modern, however, there are all sorts of things you can do, including simply shutting down the port that outside line is plugged into. Or, more prosaically, you could just disconnect it when you aren’t using it. That’s the simplest way to achieve what you are going for.

Yep, it’s a valid concern. They will be inside your network at that point, which makes it much easier to hack you.

Walk up to the switch and unplug the ethernet cable that connects to the outside. That’s the easiest way to do this. Or, get into your switch (most switches today simply use a browser and some RFC-1918 static address to allow access…sometimes it’s your gateway address, if your switch is providing DHCP) and shut the port down. Or, as another poster mentioned, a lot of switches allow you to do what’s called MAC address filtering (if you want to get fancy). Basically, only Allow computers to connect on that port (or on the entire switch) that have MAC addresses of machines you want to allow. That would be fairly secure.

I have to admit, I’m not sure what you mean by this. Do you mean 4 PORT switches? You can get an 8 port switch at any electronics store, or even Walmart. They are cheap and easy to use and install…and just about all of them have the features I mentioned (plus some more if you REALLY want to get fancy…you could set up the port outside as a separate VLAN, for instance, and do some additional security with that).

In the end, the most secure thing you could do though is just disconnect that cable from your switch unless you are using it.



ETA: Although they seem to be limited to 10Mbps, but since it’s for a network printer, they should be fine for Dog80’s application.

coughYou’d have to buy that extracough. IOW, it doesn’t come with a standard switch…which was the point I was making.

ETA: And frankly an A/B switch box is pretty old school tech. :stuck_out_tongue:


Oh, it is. It is. But given Dog’s criteria of:

-“So I am looking for a simple on/off switch that will easily disconect this run of cable from the switch.”


-“It would be possible to disable that specific port if I had a managed switch, but I don’t and besides this process will have to be repeated every day when the shop opens and closes by not tech savvy people.”

I figured the switch box is the best way to go. :slight_smile:

Sure, s/he could go that way. I still say the easiest way to ‘disconnect this run of cable from the switch’ is to, you know, simply disconnect it from the switch. It’s certainly the cheapest. :wink:


Granted, but in post #3, Dog80 said,

ETA: Okay, I’ll stop now. /bow :smiley:

Sure, but if you hook your switch box up to the wrong cable it’s going to be the exact same problem. The solution is to test which cable you are disconnecting and then simply put some sort of label on it (I’d recommend a big smiley face with a drop of blood on it) so that you know exactly which cable it is…and then disconnect that.


Sorry people! I am using the word “switch” to either mean a mechanical switch or a network switch, hence the confusion.

No, I meant a mechanical toggle 4-pole switch. I could put two of them side by side on a hobby box and connect their levers with some heat shrink tubing so they are actuated simultaneously, along with a couple of cat5e sockets and make my very own switchbox.