Question on IP addresses (help this newbie!)

odds of an exact IP address match?

[Holly_NY]

Hi there!
I am new to all of this so hopefully I will explain my question correctly. I have been looking at some rather odd activity in my server log files.

Through some reading and detective work on my part, I have come up with the IP address of my "visitor"....it just so happens to be an exact match to the IP of an existing site member.

My question is this:
When 2 IP addresses are an exact match, is there any possible way that the same computer is not involved?
I understand that it could be 2 people using the same computer...but I was just wondering how good my "proof" of 2 identical IP addresses is?
Thanks in advance for any help you can give.
Holly

[Grumpus]

It is possible for two completely different people to have the same IP at different times using a dial-up connection - you're given a new one each day. Now, if you've got this dude messing with you over the course of several days, it's almost assuredly the same person. (Or else, everyone with a dial-up connection from that ISP has decided to team and and f with your head.)

G.

[Hannu]

Hi Holly_NY and welcome!

Due to lack of IP-addresses most service providers (as AOL) use dynamic IP-addresses. This works in two manners:

1) Every time eg. a user connect to the Internet he/she gets a new IP-address

or

2) During a single session the customer gets a new IP-address for every request (eg. pageview). This is how AOL handle it.

So, one IP-address can be used of many different users.

Hope this answers yor question.

[Mardi_Gras]

Welcome, Holly_NY!

It sounds like you have already linked your member with an IP address, which leads me to believe that the member has a "fixed" IP address. That identifier would be unique, and no one else would get it.

However, someone using his computer, or in some cases someone on the same network, would be identified by that same IP. For instance, in my office, several of us share a cable connection. Internally, we have different IPs, but we show up to the world as one IP address.

If you are certain that your member's IP address is unchanging, then you are probably dealing with the member or someone in his/her organization.

Hope this helps!

[Holly_NY]

Thanks everyone!

This person is on a cable connection...not a dialup. I know with dial-in you get a new one every time, DNS connections as well.

But this is a cable modem. So, I think I have caught the rat in the trap. hahahahah

Thanks for your help, I will definitely look around the site and visit here again.

Holly

[Mardi_Gras]

But this is a cable modem

Holly_NY - Cable connections are not by definition fixed IP. I have fixed IP at the office, but at home it is dynamic. Both cable connections, provided by the same company.

That's not to say you haven't caught the rat:)

[Grumpus]

That is true about cable IP's being dynamic. Unplug your modem and plug it back in... Boom - new IP address (same cluster, but new nonetheless).

G.

[Lisa]

Look at Browser String and Operating system they use. This can narrow it down. And if you want to catch the rat in a trap, try giving them a cookie. If the rat eats the cookie and comes back later with the cookie on this face you know you have the same rat.

[Mardi_Gras]

Great idea on the cookie, Lisa. But you knew that :)

[richlowe]

Not only will you get a different IP when you drop and reconnect cable modem, many will give you a new IP each and every night as well.

Richard Lowe