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Can 2 people have the same IP address? [Archive] - DVD Talk Forum


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Th0r S1mpson
01-28-03, 02:32 PM
Okay, I set up IP tracking for a client of mine... it sends me a warning email if someone signs up for a free trial from the same IP twice.

So... there is an IP that has signed up for like 8 trials. And the guy swears he only signed up once. Is he full of crap or is this really possible?

All accounts had AOL email addresses- does AOL maybe use duplicate IP's for people?

I'm thiking this guy is full of it, but don't know much about duplicate IP's. I thought that was an easy way to tell one user from another.

Anyone know or have tips?

01-28-03, 02:48 PM
i think modem users got assigned different ip address whenever they connect. So, it is possible 2 people have same ip address, just not at the same time.

01-28-03, 03:10 PM
I have DSL, yet I have a dynamic IP. I may have the same IP for a couple weeks, or a couple of months, but eventually I'll have a different IP.

Modem users generally have a different IP each time they connect. There are a small number of IPs with a large number of customers in hopes that they'll not all want to connect at the same time.

Many companies have one external IP and split a connection between the whole office. So to the outside world, everyone shows up with the same IP.

My suggestion would be to look at a combination of things. If the free trial requires a password, check to make sure multiple signups from the same IP don't have the same password. If they enter home addresses or email addresses, key off of those. Unfortunately, nothing is foolproof.

01-28-03, 03:41 PM
does he have a brother?

01-28-03, 04:01 PM
His brother is spoofing the same ip address :lol:

Possible yes, likely no.

01-28-03, 04:19 PM
Yes. Some ISP's use private IP ranges and so only the public IP on the outside end of the router is detected.

01-28-03, 04:42 PM
I believe AOL users actually surf the web from behind proxy servers, so yes, many AOL users will appear to share an IP.

Also anyone behind a NAT router will share external IP's. Lots of companies use this and of course many families as well.

01-28-03, 06:33 PM
Basically the last post is correct.

When people or companies sign up for internet service they are often given one or a few IPs. They can share this using a router or a NAT server (network address translation). Basically the router routes the packets through this one IP out to the internet and from the internet it finds the correct computer on incoming packets.

So short answer is yes, it's possible different people can have the same IP.

01-28-03, 09:21 PM
You especially have to watch out for AOL IP addresses. On my discussion boards, we've had problems with people signing up for dupe accounts from AOL IPs, but you can't block them because a lot of AOL users share IPs.

Also, if you're behind a router, you'll share an IP. I share the same one as my roommate - just the way a router works...

Th0r S1mpson
01-29-03, 01:29 AM
Yeah, these are all AOL addresses. And there are now 12 of them with dup. IP's. That's out of about 150 total members which is why I found it suspicious. It's like AOL only has one IP or something.

Since people have posted here that this is typical with AOL accounts I guess I won't throw any flags. The free trial ends soon any way. I can look at other factors as suggested to see if there are signs of duplication.


01-29-03, 09:24 AM
You could just say that the free trial is unavailable to AOL users, since such neophytes probably won't get much use out of it anyway.

j/k! (sorta) ;)

01-29-03, 12:28 PM
I know that for my company only one IP address is used to connect to the internet. The proxy server handles all of the traffic therefore the need for only one external IP address. AOL IP addresses, as I understand, are Dynamic (assigned as you connect/recycled). This creates the possibility of multiple users being assigned the same IP at different times.

03-24-03, 02:01 AM
how can i spit an address into two? i play a MUD and i am trying to get brother to play aswell but can't cuz we share the same ip. we have 3 comps connected to a wireless router (linksys), the main comp uses win98, mine and my borther are both xp. he was going to call comcast and get a second ip addy for himself which would of sovled the problem but he decided against that, didn't want to pay for it. so is there any other options?

03-24-03, 02:06 AM
contact the people that run the mud and explain the situation.

03-24-03, 02:10 AM
i'm not sure that will help. if there is someway to just tag the acutal comp with the ip that might work but i don't know if they can do that. basicly the mud allows you two connections, 2 characters. my brother and i are on now but only with one character each. if they just let us slide, one player could be controlling four guys, which they would never allow. thanks for the response though.

03-24-03, 10:19 AM
i haven't even logged in to a MUD in years, but years back when i used to get the "my 'brother' wants to play too" story we were always really skeptical. maybe in this broadband era it's more likely to get sympathy, but i'd guess most admins will stick to their policy of 2 characters per IP or there will be a sudden influx of "brothers" from every player out there :>

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