How do people know the IP addresses of others? On another site, I was told that the reason someone else got banned was that she had the same IP as another guy (having more than one account is against the rules there)... he wasn't staff or anything, how would this person have known her IP address?

9 out of 10 sites nowadays can track the IP's of users that use them. Thats pretty much common knowledge now

But how would this guy in particular know her IP address? He doesn't own the site, or have access to their database as far as I know...

When your browser sends out an HTTP request, one of the things it has to send is your IP address, so the server knows where to send data back. Therefore, anyone with a server can gather IP addresses; this actually includes the ability to add images to forums because you can have an image that forwards the request to wherever the image is hosted (you've probably seen the signature images that say your IP). Various lookups allow you to take an IP address and match it with an ISP and general location. This is how banner ads can show advertisements, for example, for hookers in your town.

With regard to two people having the same IP, most people are on cable or DSL these days. Whenever you reboot your router and connect to the Internet, you are randomly assigned a new IP address from a set that's been allocated to your ISP and area. Therefore, it's possible for two people to have the same IP totally by coincidence (though not likely).

I'm not really sure what you're asking though.

Some ISPs don't give out a new IP address every time you connect. Some only change IP addresses when they do upgrades, etc. The ISP I currently get my connection from does this.

The other person could have just heard that she/he got IP banned. Might have got banned cause two accounts had the same IP. He didn't have to know her/his IP to say he/she was IP banned.

The site specifically states in their rules that they DON'T ban by IP. Anyways I've gotten advice from about 4 other sources by now, and all of them say that this guy is just trying to mess with me... what a surprise .

Or at least say they're from your town

You would know otherwise?

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The site specifically states in their rules that they DON'T ban by IP. Anyways I've gotten advice from about 4 other sources by now, and all of them say that this guy is just trying to mess with me... what a surprise .

I still don't understand your specific question with regard to this site.

Sometimes the ads say I'm from Canada or something

An IP address is public information. If it wasn't made public, you wouldn't be able to connect to the internet.

Maybe your ISP runs in Canada too.