We have a crowded computer laboratory. We render free Ethernet ports for laptop users. But they don't carry their Ethernet cables with them, they unplug cable of a fixed desktop PC and plug it to their laptop. When their work is finished, they don't even plug it back to the PC. Worse than that, after a lot of plugging/unplugging, physical damage occurs on the Ethernet ports of the fixed PCs. At the moment, we have three computers whose Ethernet ports are damaged because of this.

How do I prevent people unplugging the Ethernet cables of the fixed machines?

  • 7
    Why not lock out non-lab computers from getting a working connection?
    – Adam V
    Jan 31, 2013 at 17:41
  • 31
    You could also offer wifi, can probably find a wireless AP for about $100. Jan 31, 2013 at 19:46
  • 18
    Krazy Glue and Duct Tape Jan 31, 2013 at 20:21
  • 13
    Might I recommend converting some select cables to Ether killers with a 'Danger! Do not use/unplug!' sign on the cable. Plug them into dummy ports on the PCs and let them play Russian roulette with your network cables.
    – Mokubai
    Jan 31, 2013 at 21:29
  • 9
    Why don't you just stump for a small pile o' spare cables...? Feb 4, 2013 at 8:35

19 Answers 19


I think this might help you http://www.rjlockdown.com/patchcordpage.html

enter image description here

I was looking in buying something like this a while a go, but I never did, but it seems to be what you are looking for

  • 2
    I have used these before, and they're a simple solution to a simple problem. They work quite well, and are reasonably priced.
    – MDT Guy
    Jan 31, 2013 at 18:19
  • allen key ?! if they had a real key, this would be a good solution
    – Sirex
    Jan 31, 2013 at 21:02
  • 2
    @Sirex - I'd say this was still a good solution. How many people carry a set of alan keys everywhere with them? And the chances are if someone would be that meticulous, they probably have the 'nouse' about them not to damage ethernet ports when plugging/unplugging cables.
    – Anonymous
    Feb 1, 2013 at 16:49
  • 21
    maybe. i'd say 'how many people carry allen keys' is answered by 'the number of people who have used the lab more than once and found last time that they needed an allen key to remove your cable'.
    – Sirex
    Feb 3, 2013 at 2:33
  • 17
    How many people will not notice the difference and just try and rip the cable out doing more damage than before?
    – user195344
    Feb 4, 2013 at 10:16

If you are looking for a cheap and easy way to do this, just use zip ties. You can put one near the end of the ethernet cable, one somewhere on the back of the fixed PC (like to an open vent or empty card slot), and use another to connect the two. It wouldn't keep the cables from being unplugged, but it would prevent people from moving the cable more than a few inches from the PC, rendering it useless to use on their laptop.

zip ties holding ethernet cable in place

  • Funny thing is, I don't think I've ever seen this done, its just the first thing that popped into my head.
    – Kibbee
    Jan 31, 2013 at 15:49
  • 2
    I'm not sure how well this would work. First couldn't you force the cable through the loop. Second those little zipties are typically only rated for 25/40lbs; snapping one by hand isn't hard; and jamming a pen/cil into the small loop where the one ties onto the case would probably work even if you don't have the strength needed to rip it free. Jan 31, 2013 at 17:10
  • 13
    You're never going to stop someone who's determined to take the cable. They're more likely to damage the cable than the port trying to remove this, so it should be enough to deter most people. The "connector" tie is probably the weakest point, as the other ones are too difficult to get at w/o a cutting tool of some sort. You could simplify this by just using 1 zip tie and securing the cable to the case directly.
    – techturtle
    Jan 31, 2013 at 17:31
  • Do a search for stainless steel cable ties and all you have to worry about is people destroying the cables trying to get them free. Make a little sign with a picture of Wolverine saying "ADAMANTIUM CABLE TIES - YOU WILL NOT FREE THEM" and you will be fine. You can also wrap the cable connector sections in tape and make it even more difficult to fool around with.
    – nvuono
    Feb 4, 2013 at 13:54
  • Instead of using cable ties, just use one of these, loop the cable through and affix it with a self-tapping screw to the metal case. Obviously, make sure there is clearance under the panel so you do not screw it through the CPU…
    – sleblanc
    Apr 17, 2015 at 23:44

Don't fight; be polite.

Instead of fighting people who want to use the internet, make it easier for them to use the internet without interfering with the desktop systems in any way.

The first step to keeping people from doing things you don't want them to do is to ask them nicely.

  1. Put a sign on the back of desktop systems asking people in need of ethernet cables to request one from the lab attendant. you can still ziptie the cables to the desktop, but that won't stop anyone with a penknife or pair of scissors.
  2. Get some cable. I recommend buying a large spool of ethernet cable, a set of crimpers, and some plugs. I recommend this over buying pre-made cables as it tends to be much cheaper, and you'd be able to make cables in whatever size you need. Most people shouldn't need more than a few feet of cable if the ports are close to desks. If people steal their cable, it'd be much cheaper to replace. Instructions on how to crimp an ethernet cable can be found all over the internet. It's remarkably easy to do.
  3. Attach a sticker to each cable that asks the borrower to return the cable to the attendant when they're finished.
  4. Give cables to people freely when requested. This is the most important part. They need a cable. If you meet their needs, they'll no longer have a reason to steal cables from other machines. You could set up a bartering system where they give you something (like a shoe, bag, or ID) and they get it back when they return their cable. I don't like this solution as it makes it easy for the lab attendant to get in trouble when someone's stuff gets stolen if they happen to go to the bathroom.
  5. Ask people to donate spare cables to support the lab. If you're giving away free cables, I'm sure there are others who have some lying around from their old router or computer.
  • This works with some percentage of people. Others don't care or simply assume resources will magically appear from the lab to replace the ones stolen or damaged--an assumption reinforced by the continuous replacement of stolen or damaged resources. There are locks which visibly lock the RJ-45 connector to the port and can't be removed without a special tool. Hotels now use them for their VoIP phones and other internet connected room objects.
    – Jim
    Nov 4, 2016 at 22:34

Cable ties are a great idea, but they can be easily cut with scissors or a knife.

An alternative I have used in the past is to trim the release tab back to the point where the cable will still latch into the RJ45 port, but the tab is not accessible to release the cable. This then requires a tool to release the tab because its recessed.

Cut at the red line (approximate). You may have to adjust cut location to suit your needs.

enter image description here

  • 19
    Clever. I've had cable ends break this way on their own, and I can attest that they are very hard to get out. You would run a higher risk of damaging the port even by someone authorized to remove the cable, though.
    – techturtle
    Jan 31, 2013 at 17:34
  • 5
    "Cable ties are a great idea, but they can be easily cut with scissors or a knife. " If you assume users with knives to hand (you should, I have one more or less all the time) then these same users can as easily circumvent this as the cable tie: tip goes in, cable comes out. Perhaps more easily as the motion to release the jack is small and require no appreciable strength. Jan 31, 2013 at 19:36
  • 2
    Valid points. Not saying the other suggestions are not good. Was just sharing my experience and what I found worked for my situation. There is no correct answer for this question because everything depends on the determination to GET the cable.
    – CharlieRB
    Jan 31, 2013 at 20:41
  • fwiw: you can hook the cat5 latch out with a pin.
    – Sirex
    Jan 31, 2013 at 21:00
  • 4
    I have seen the not-so-techincally-astute simply yank really hard after a point. They assume it doesn't lock in because there's no "unlock" tab to press.
    – Izkata
    Feb 1, 2013 at 4:27
  1. Provide more dedicated for-laptop cables;
  2. Integrate system units somehow to make cabling inaccessible.

I think with enough cables + Wi-Fi users should not need unplugging Ethernets from PC.

  • 21
    +1 for #1. All the other solutions will fail because the universe's ability to create idiots always wins. Jan 31, 2013 at 18:11
  • 8
    I tried the more cable solution in praxis. My users always took the cables home and never brought them back. After a a few dozen cables I gave up on it and returned to tie wraps and glue.
    – Hennes
    Jan 31, 2013 at 18:26
  • @Hennes: So now you need some way to discourage users from stealing the cables. I'd suggest zip-tying each spare cable to some fairly light but bulky and/or inconveniently shaped object (say, a 2' plastic stick) that has "PROPERTY OF <INSTITUTION>, DO NOT REMOVE FROM <LAB #>" written on it in large letters. Jan 31, 2013 at 18:43
  • 6
    Or, you know, just change the "fixed" PCs to use Wifi. Can't unplug them if there's nothing to unplug.
    – Mark Allen
    Jan 31, 2013 at 20:36
  • 11
    Stealing the cords won't be an issue if, like most computer labs, only one end of the cord is accessible. Usually the other end is plugged in inside a cabinet under/between the tables, or runs along the wall to god-knows-where. Feb 1, 2013 at 0:46

I don't envy you your user base, but still, look at it from their perspective: To use their computer lab, they have to carry a cable on top of all the other junk they need to get through their day. So, they borrow a cable from a PC and often forget to plug it back in-- or maybe they leave it free as a courtesy to the next user. The ones who took the free cables home have no excuse, of course, but they were doubtless a minority.

So, what to do? Instead of going to war with your users, solve their problem and they'll have no reason to mess with your equipment.

  1. Wifi. It's 2013, dude. If I was forced to use a cable I might get uncooperative too. If access by people from outside the lab is an issue, lock it and post the password on the wall.

  2. If wifi is really out of the question, provide new ethernet cables and lock them to the wall. If there's nothing to attach a zip tie to, bolt something to the wall.

  • 1
    Not just Wifi, Good Wifi. And only set a password if there's a need for it. I've seen too many Wifi deployments collapse under load or greet you with a password page every 5 minutes. I still prefer to take a cable when that happens. Feb 1, 2013 at 0:16

There are cables with built in locks.

Check out LockPORT. They make secure cables that require a special tool to be removed.

enter image description here

  • 1
    What happens when someone tries yanking it hard thinking it's just stuck or tries to overcome the locking mechanism via brute force? Jan 31, 2013 at 17:12
  • 7
    They would probably break it. But I don't think he is looking for something super secure, I think he just wants people to get the hint not to unplug them. Just like anything, if someone really wants to defeat it they will find a way. This is more of a deterrent for the typical lazy person who just unplugs the nearest cable.
    – BroScience
    Jan 31, 2013 at 17:16
  • Have used this and teh RJ LOckdown device and both work well. As @BroScience mentions, enough force will break either but that is a sign of a different issue
    – Dave M
    Jan 31, 2013 at 17:30
  • 5
    The OP's primary reason of concern appears to be damage to ports on the desktops. That's something that would only happen because of people yanking the cords out abusively. This seems likely to deter the people who unplug the cables correctly; but not the idiots who're yanking the cables out violently enough to damage hardware (because they don't understand they're supposed to press the clip to release them, or just don't care). My concern is that locking the cables in more tightly will increase the likelyhood of them breaking ports before figuring out their stupidity won't work. Jan 31, 2013 at 18:11

A large number of physical solutions have already been provided, so I would like to give a software one that can, of course, also be used in addition physical measures.

Put some kind of port security up (preferably 802.1X) - while MAC whitelists can be relatively easily circumvented, I'd like to see someone circumvent 802.1X without physically disassembling your lab machines.

Also put up a sign explaining that removing the cables is now only good to make The Sysadmin angry, and that they won't like him when he's angry. (Public display of a LART is highly recommended.)

If you have BOFH inclinations: Make the cables work even for unauthenticated users, but assign them a special IP range. Log access to any authenticated services from said IP range, and lock the user accounts. This way, they'll come to you to pick up their punishment, and you don't need to constantly watch the logs and immediately sprint to the correct location for catching the person (you still may want to do that for the added "all-seeing admin" effect). Or just redirect everything to a login form, and connect it to a "lock account on correct login" script. You will be amazed how many users are dumb enough to try. (Originally, I wanted to suggest simply blacklisting their MAC so their laptop doesn't work anywhere on the network, but since MACs can be faked so easily, this could both be easily circumvented and lead to nasty pranks.)

If you are nice and want to provide cable-based access: Do what my university did, add a second NIC, add a 1.5m network cable to it, and route/bridge/whatever it to the network. (All cables behind the PC go through a giant zip-tie to make stealing cables, mice etc. harder.) In my university, the users have to log in on the PC and activate said cable there, making sure only authenticated users can use it and all access can be attributed to a user. Unplugging the "uplink" cable from the PC and accessing it directly is prevented by 802.1X, as far as I know.

  • Another possible, non-hardware solution. Have the computer make loud noises once the cable becomes unplugged.
    – avgbody
    Feb 4, 2013 at 19:32

Use a cable-tie and somehow secure the cable to the case, possibly through an empty PCI slot, or some other hole in the case. Place the cable tie as close to the end that clips into the PC as possible. Then wrap tape around the other side of the cable right next to the cable tie so that it can't slide through the cable tie. Combine that with having a few cables available for people to use with their laptop as @Vi. recommended and you'd probably stop a lot of this stuff.


Change the fixed PCs to use WIFI, which will

  • Render them unable to be unplugged from the network, since there's nothing to unplug.
  • Free up those three cables for laptops.

You appear to be solving the wrong problem. Your problem is that you are not providing an appropriate method for your customers to connect to their network.

Offer WiFi, offer additional patched ports and put cat-5 cables in the vending machine.


Have you considered providing cords hard-wired into the wall (or at least secured to the outlet by any of the methods suggested above), instead of ports, for the "free ports" you provide for laptop use? Then they won't have a problem if they didn't bring a cable.

Since part of your problem seems to be people yanking the cords out rather than correctly detaching them, any solution involving securing the cords to the computers will just make them yank harder.


Students who have forgotten to bring cables should be able to borrow them from some lab attendant or IT desk for a cash deposit which is high enough that if the cable isn't returned, it can be regarded as a profitable sale.

To detect that a cable is being wrongfully unplugged from a PC (or that a PC has shut down or crashed), you can give the PC's static addresses and have a little daemon program ping all of them periodically and generate an alert e-mail.


one thing not mentioned yet that I've seen used: superglue.
yes, some IT departments use that to prevent people opening or unplugging computers.

  • 2
    And what happens when you legitimately need to service one of those computers? Jan 31, 2013 at 20:30
  • You'd dissolve the glue using nail polish remover (acetone) i guess.
    – Sirex
    Jan 31, 2013 at 21:04
  • @DarrelHoffman service? IT departments like that don't do servicing, they replace. So the cable gets cut and a new connector crimped on, which is then glued to the replacement computer the very few times I've seen it happen.
    – jwenting
    Feb 1, 2013 at 4:55

On top of the zip ties solution, that is actual brilliant simple, i would suggest to block internet access trough the cables reserved to the pc's MAC address. Most routers support this function. (You will either need a separate router for the desktop pc's, or one that support blocking access per port.)

Next, you place the router out of reach so the users can't move the cable to another port/router.

Actually, i would suggest you place all ports out of users reach, and only let a few meter of cable come out of the wall, that way they can't even forget or steal a cables and take it home.

Also, you can offer wifi beside cabled access. This would take some tress off the cables, while at the same time the cables take away some stress from the wifi as you wont need 40 people in a small are on wifi. Users that need high speed will still find a cable, but for most uses wifi will be more then enough.

  • This will not work. mac addresses are trivial to fake (to be the same as your class desktop pc).
    – Sirex
    Jan 31, 2013 at 21:06
  • 2
    1. Users have to figure out the pc's mac address. They even have to come up with the idea the problem lies in the mac adress. 2. It's not total security, it's just adding an extra loop to jump trough. Same as adding a zip tie, or hanging up a sign that warns users not to unplug desktop cables. You can never have 100% security in these situations, if somebody starts whacking the place with a sledgehammer things will break, but that's beside the point.
    – Dorus
    Jan 31, 2013 at 21:57
  • It's not any security. When nabbing a cable for a laptop, cloning the mac was the first thing I did on the off chance of switch port security being enabled. It'll take about a day for the kids who know how to do that to tell the kids who don't.
    – Sirex
    Jan 31, 2013 at 23:07
  • 1
    One day is pretty much the right timespan. I know because this exact thing happened at my school a couple months ago: One kid thought "Hey, I'll plug my laptop in", realized he needed to change the MAC; a week later, tons of people were doing it.
    – cpast
    Feb 1, 2013 at 5:12

Have a spare Ethernet cable plugged glued in to every wall socket. If they don't need to take a cable, they won't cause any damage.

  • And when that cable breaks? I suspect anything involving glue is a bad idea because cables used by the public break often. Feb 4, 2013 at 8:21
  • When it breaks, glue it back together! :-D But otherwise, yes, valid point. Feb 4, 2013 at 10:33

Have the switch disable access to the ethernet port upon connection loss. Then kick whomever made you come reconfigure the switch in the ass.

Alternatively block specific mac addresses for the ports designated to the provided machines.

Both of these require a managed switch.

  • Problem is that this might trigger if the PC is rebooted.
    – Kaz
    Feb 1, 2013 at 0:11

Fashion a sheet-metal cover for the port area, with a slot to allow the cable to pass.


After Looking at the RJ Lockdown device, it looks like a great and cheap option. If you decide to offer spare patch cables, you might want to try the Mono Price website Their prices are so cheap I suspect there would be no point to buying a roll of cable and building them. Also it boils down to two things Making the internet access harder to get when it comes to people using your cables that are already in use and also making it easier by offering guest wifi. If is easier and more convenient, people will most likely go with it.

Netgear offers a line of routers that offer both internal LAN access to the WAN and also a Guest Wi-Fi which you can even setup to have each wireless device to be isolated from the next thus making it more secure for the guests. Now if you placed a sign informing your guest of these changes and security enhancements, that should convince them to use the guest wifi.

An example of the router I was referring to would be the WNDR3700 or higher like WNDR4000, just Google the term "Netgear WNDR3700" or go to the Netgear site to have a look and I think you will find this will make you life a lot easier.I have placed a link to the Netgear site in my response for your convenience Netgear website

Good luck

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