ip addresses - is the same ip address assigned to every computer all the time?

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does my computer have the same ip address all the time, or does it change it dynamically?
I have a web site which need to identify the users from the information derived from the computer they are looging into the site. Is it posssible to do this?
Please advise me. :(

Posted 25-Mar-11 4:07am

noviceTaken

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3 solutions

Solution 1

does my computer have the same ip address all the time, or does it change it dynamically?

Depence on your provider, most providers use a DHCP that will reset once a few weeks, giving you a different IP adress. But some don't, most of the time this is a special internet-offer for businesses.

I have a web site which need to identify the users from the information derived from the computer they are looging into the site. Is it posssible to do this?

Yes, you can do this. You can use their ip-adresses or use cookies...

Posted 25-Mar-11 4:26am

willempipi

Updated 25-Mar-11 4:27am

v2

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Dalek Dave 25-Mar-11 10:29am

Sums it up nicely!

noviceTaken 25-Mar-11 11:42am

but if ip addresses are assigned dynamically - then you cant use ip addresses to distinguish users can you??

wizardzz 25-Mar-11 13:44pm

novice, you just answered it in your question, think about what you are saying. Can you use any id that changes as an id in anything?

noviceTaken 25-Mar-11 13:49pm

willempipi - "Yes, you can do this. You can use their ip-adresses or use cookies..."
this CANT be done,because ip addresses keep changing!

willempipi 25-Mar-11 14:37pm

You are correct, but you haven't said anything about the usage, for some applications it is enough to use the ip adress, for example a kuddo counter.

noviceTaken 25-Mar-11 14:49pm

ok thanx for your comments..and just for your information..I wanted to know if ip addressess could be used to defend myself against sybil attacks/ sock puppet accounts. i.e. having some way to identify if the same person is creating multiple accounts from the same computer..

Solution 2

Depends on your ISP and your settings.

You can have the option to have a dynamic IP, (recommended), or a static one.

Everyone has their preferred option.

Posted 25-Mar-11 4:29am

Dalek Dave

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OriginalGriff · Accepted Answer · 2011-03-25T04:42:00

Solution 3

To add to the other responses, if you do not specify - and most people don't - then the ISP will assign a dynamic IP address - but that isn't the IP of your PC. It is the IP of your modem. If you have a number of people sharing the same internet connection (normal for a work place) then they will all have the same IP, with a different subnet address. So I could log in and have the same IP as the guy sitting next to me.

The dynamic IP address will be renewed whenever the modem is re-started. So I could log into your site, turn my modem off and on again, and come in on a new IP.

Use Cookies.

Posted 25-Mar-11 4:42am

OriginalGriff

Comments

noviceTaken 25-Mar-11 11:35am

"but that isn't the IP of your PC. It is the IP of your modem."
- so is there a way to get the IP of your PC. because cookies can be blocked by the user, in which case there is no way to identify whether its the same person loggin in/ creating multiple accounts.
what about 'user agent strings'? There has to be a way to uniquely identify users right??

OriginalGriff 25-Mar-11 11:55am

That's why so many systems rely on cookies and email addresses: you can't uniquely identify a user by any means: even the MAC address only identifies the individual PC networking components (and you can get that if the client is running IE, not FF or Chrome) So if the user has access to multiple PCs (and I do for example) then that isn't going to do it. There is a description of how here: http://www.eggheadcafe.com/community/aspnet/3/10054371/how-to-get-client-mac-address.aspx - I haven't tried it, so don't blame me if it doesn't work!

Basically, there is no way to prevent "sock puppet" accounts.