How do I stop my neighbor from using my IP address?

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"...important to note that your neighbor could be completely unaware...".
Excellent point, Leo. You truly stand out in the advice sector. That little comment probably has 50% of your readers relaxing. Put down the AK47s and tomahawks, folks, most things done by newbies are unintentional.
Amazing how many folks immediately think the worse. I run into this most of the time. It is never their "fault" for not following protocol or just simple tried and proven good computing steps.

Goos advice, Leo. Kudos.

Awwwww, how did you know I was going to suggest putting a hatchet in the neighbor's computer? :-D

A question that came to me in the first place was "how did the guy know his neighbor had used his IP address?" It's not exactly displayed by default in any email program (local or webmail) I've heard of. And since I have DHCP, I generally don't know what my IP address is at any given time; I usually go to http://www.whatismyipaddress.com if I even need to know. (Hey, Leo! Another tip! "How to find out what your IP address is!")

If only I had an article on that already. Oh wait! I do! What's my IP address? (That search function is a wonderful thing.)

- Leo
20-Jul-2009

Weeble - it's been done: http://ask-leo.com/whats_my_ip_address.html

It's not so good that in the US, routers are often configured with unsecured wireless access and it's up to the user to create an access key. My Fritzbox router in Germany is preconfigured with a unique key printed on the router. The number can be read by anyone who has access to the router, but until I know someone has compromised this key (detached the router and copied the number) I'll stick with it as my kids are often changing computers and in spite of the small risk, the convenience is worth it at the moment.

It still amazes me (though to a lesser degree) how many people simply plug in a wireless router and go. At the moment, my laptop sees three SSIDs of "linksys", all unsecured. Out of curiosity, I have on occasion, connected to one of them, brought 192.168.1.1 up in my browser, and logged into the administrator control panel using the out-of-the-box login and password. Good thing my morals prevent me from doing anything malicious.

Another Point to Remember - Make sure you keep your Network Security password ID written down in a safe place in the even you forget it. Also, when setting up your encryption - make sure you do your homework first- as some older wireless cards may not be compitable with some of the newer encryption. If you like online games - check this out: [link removed]

If the neighbor is in fact sharing a wireless connection, and that connection is like my Linksys Wireless Router, the local router will get an IP address from the ISP and then assign a DHCP address to each unit on the local network. Commonly this is in the default range of 192.168.1.xxx. The 192.168.1.xxx range of IP addresses is "not routable" and will not be passed across the router to the outside world.

To the outside world (on the other side of the router from the local network) there is a single IP address assigned by the ISP to the router port directly connected to it. The router determines which local IP address is involved in the transaction and passes the traffic through to the appropriate hidden and non-routable local address. That is part of what routers do.

So from the outside world perspective, every unit served by the local router appears to be the same IP address that was provided by the ISP.

The result of all this is that anyone who sends an e-mail from the local network will appear to have sent from the same ISP assigned IP address that is assigned to the port on "world" side of the router and to be using the ISP assigned address. The 192.168.1.xxx IP addresses are not disclosed across the router to the outside world.

This is a probable answer as to why the addresses are the same.

The other comments about the neighbor's use of the same wireless network by design or ignorance are germane. Appropriate wireless connection security is the answer.

Another good tip to stop a neighbor using your IP address, is to set up an access list on your router, that is of course assuming that your router supports this.
An access list will allow you to limit the devices that can access your network by specifying their MAC addresses.

I agree with Gary, I found the easiest way was to specifiy the MAC addresses in the router set-up. Most modern (last 5 years) routers seem to support this.

You still did not answer the question-how he knew his neighbor was using his IP address. I am curious to know that.

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