IP address of network computers

edpudol

hello again group!

I am creating a website that visitor can vote but I want that 1 IP address should vote only once, this problem solve, but my problem is how can I determine if the entry is came from a network of the same ip address.

What I mean is, for example the visitor rent from a internet coffee obviously the computer he/she use is connected to other computers with the same Internet Service Provider.

Hope you got my point, sory for my poor english..

once again thank you

TheDefender

This is the common problem with using IP addresses for this kind of stuff... People behind Firewalls, or surfing from within Proxies.

OK, here's the scenario. At my work, we run a PIIX Firewall, and all network traffic outside of the Firewall comes from 1 IP Address, so in theory, only one person from my office could use your poll.

You can't circumvent this and determine if it's a different computer by looking for their internal IP Address. If you could do this kind of manipulation, then you'd be a huge risk to my network, because then you could (in theory) come in through my firewall, and talk to my computers directly... This isn't going to happen. That's why I have my firewall in place.

The only way to really do this is to write a cookie to the user's PC when they vote. Then when someone else from the same IP comes in, you could look for that cookie, and if it exists, then you know they already voted. Otherwise, you let them vote. Obviously, this could be bypassed by the user deleting their cookies... But a poll on the web is not nearly as important to companies as the security of their network behind a firewall.

edpudol

So is it mean that network computers with 1 Internet Service Provider use diff. IP address when they logon on to the net with out determining their IP address and if yes is this computers use the same IP every time they logon to the net?

Thanks...

Weedpacket

Originally posted by edpudol
So is it mean that network computers with 1 Internet Service Provider use diff. IP address when they logon on to the net with out determining their IP address and if yes is this computers use the same IP every time they logon to the net?

Thanks...

If by that you mean the same person could be hitting your site from a different IP address during different sessions, then yes. The proxy server will have a whole block of IP addresses to choose from when passing along a request, and in principle could use any one of them for any request at any time.

TheDefender

I don't fully understand your question, but let's use my work network. My firewall shows one address to the outside world... On the inside, the PCs are in a class C (192.168.x.x) configuration. Your script would only see the 66.152.x.x address regardless of the inside address... The inside addresses are handed out by our domain controllers, and rarely change. My work PC has been the same for a year now.