IP uniqueness question

If their provider (ISP) uses dynamic IP addresses (quite common), then they could be sharing a pool of a few hundred to many thousand addresses at the same time. You only get a unique address if the provider and the user are on a static IP address.

 

I've always wondered about that too.

How about ISP customers who live in the same location, or colleagues at a company using DHCP. Can they get their neighbor's IP and vice versa, if they reboot every now and then?

~shahedc
.

 

+1

 

Joe,

I'd look into other factors besides the IP for the coupon issue. Depending on our order process/backend fulfillment checks, I'd look at other fields for similarities in the orders. ZIP codes might be too broad, but if you can pull up a list, or even audit it on a daily basis: Orders from 77777 and glance for duplicates or similar names/addresses, etc. Otherwise, if you are looking for one computer to not duplicate an order, you'd just want to set a cookie, but you can get around that with a different browser on the same system.

Next idea - which is also dependent upon your backend system - a generation of unique coupons for each user to redeem and they can only be used once.

 

With 99% of your visitors, IPs are newly generated by their provider when they logon. So it is not only possible that the same address will be used by someone else next time, the probabilty is near 100%. Static IPs are very rare (of course they are tied to servers, but servers don't visit your page ), only like big companies have them, and then there are hundreds of people surfing with that adress as normally a huge (company) network resides behind them.

 

This may be too easy... how about using the customer's shipping/billing address to verify uniqueness? If it's 1 per household, then that would be the "correct" way of verifying that.

And if they use one or more address, you really can't prevent that. At least they are going out of their way to order your product. (but they don't like it enough to pay full price multiple times)

 

I guess that IS the way to go. Be sure to randomly compute the coupon codes, use numbers and letters (like MA4Z39D) so no one can just type in a number and benefit from your offer

 

NAT and SuperProxies make relying on end user unique IP addressing impossible.

The correct answer is probably setting a cookie or requiring login that vets addresses for uniqueness.

-dsd