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The Situation

When im staying at my girlfriends we both like to have internet access on our laptops but her accommodation don't allow wireless routers.

My Question

My question is if I set up an Ad-Hoc network to share the internet connection as shown here on How To Geek. Will my laptop be acting as a wireless router or will the connection all go through my laptop as one ip address so it appears to be my computer accessing the webpages etc, that my girlfriend actually is.

  • i would be interested in knowing any additional information that could help sove this problem eg. if connectify would do what i want.
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An important question might be why do they not allow wireless routers? Is it just routers in general, or the wireless bit that's a problem? Though I doubt you'd live in an "RF Quiet Zone" and not know it, this may be something to consider. – Iszi Apr 11 '12 at 20:39
I imagine its routers in general, and I can only assume its to do with there being a limit of one IP per apartment tenant, or perhaps its so people aren't idiots and give away the internet free to anyone in range, I don't know. People have been fined for it before so I don't want my girlfriend to get fined...I did it anyway, works fine. I told her if they start asking questions to just say she connected her phone to her laptop via WiFi so she could use the internet on it...seems like it would be reasonable enough...also promised I would pay any fine that might come her way. – Jacxel Apr 12 '12 at 8:17
hoping it is not too late, you may wish to read my reply as well. – MariusMatutiae Jun 11 '14 at 7:14
up vote 1 down vote accepted

If you want to respect the spirit of an ill-formulated rule, then there is no way that you can do this. If instead you are willing to break the rule, provided you don't get caught, read on. But the choice really is all yours.

Any connection you mentioned, the wireless router or the Ad Hoc network, is liable to detection by a simple wifi scan. In either case, the service provider will see only one IP being connected to the network, but she can reveal a new, unknown network and assume someone's not playing by the book. In line of principle, it can even get worse, because it is possible, with the help of a GPS device, to pinpoint the origin of the new wifi network, though this is not very common. Also, there are common techniques (aircrack-ng) to identify which pcs are connected to which APs (Access Points), without any need to connect to either.

You might be able to mitigate the problem by decreasing the transmitting power of both the pcs and the AP (be it wireless router or Ad Hoc network), even though this has other drawbacks, or by choosing the less common 5GHz band. Yet none of this is fool-proof.

The only safe way to allow multiple users would be to connect to the wireless router by cable, for the both of you because there would already be the IP of the router.

Even this requires some adjustment, because the router, upon connection to the home network, identifies itself by MAC address, which carries information about the manufacturer. A savvy tenant could then see connected to her network a component produced by Ciso/Linksys/D-Link/TP-Link, whatever, and would know immediately that her bandwidth is being used by a router plus several connected pcs/phones, ... This can be easily circumvented, because most good routers have a feature called Clone MAC address allowing them to broadcast a user-defined MAC address, and all you have to do is to chose, for instance, an iPad MAC address.

Still, you may argue that your tenant is not very computer-savvy, otherwise she wouldn't have formulated such a silly rule. What she is trying to do is probably prevent any single user from hogging up all of the bandwidth, a concern which can be addressed with much more sophisticated instrumens (tc, anyone?). So, if you are willing to take the risk on the basis of this argument, with the proviso stated above about MAC cloning, you might think it safe to implement either option (wireless router/Ad Hoc network), the only distinguishing feature between the two being that the Ad/Hoc network emits a weaker signal, and is thus more unlikely to be detected upon casual perusal (if the perusal is determined, there is no way whatsoever).

Hope this helps.

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Setting up a computer to provide internet access to another computer via Internet Connection Sharing will work off multiple IP addresses.

Hmm... Ok. Internet Connection -> First Computer. That computer gets an IP address from the Internet Connection device and sees the Internet Connection as a Gateway. Now... if you set up ICS (Internet Connection Sharing) to share that internet connection across a second network card (Wireless or wired, doesn't matter) ICS will want to work on a different internal IP range, and set up that first computer as ANOTHER gateway.

I'll put it another way. Let's say her laptop is connected via ethernet cable to the internet connection in her apartment. Her laptop gets an IP address of You set up her laptop to share that internet connection across her wireless card. This will require also enabling ICS. ICS will assign the IP address of to the Wireless Card, and make it a Gateway. If you connect your laptop to this new Ad-Hoc network, you will get an IP address on that new range ( maybe) and your computer will now be seeing as your internet gateway.

Some details? The computer that is going to be in the middle has to have two network cards (two wireless, one wireless one wired, two wired) where one is connected to the Internet Source, and the other connects to the other computer.

The computer in the middle will not act as an Access Point, just passing out IP addresses in the existing range that is offered by the internet source. It will indeed act like a router, starting a new IP range.

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As an alternative, this answer applies to your situation alone and is technically against the rules but worthy of a mention.

If they don't see the network then it's unlikely they will be able to do much about it. You can just disable the router broadcasting it's SSID (Network name). This will make the routers WiFi invisible to those who don't already know it exists (or running Kismet but I won't go into that). Connecting to it just requires entering in the SSID into your laptop upon initial connect. It should be able to find it afterwards.

This is of course the more sneaky approach to your problem.

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