>>>As you correctly indicated, I am getting "::1" for IP when running on my local Web Site. Do I understand that when I deploy the app to the customer web site (and they will hit it not from local web site), I will see valid IPs?
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>>You will see a valid IP if your site responds to the Internet.
>>
>>Note that you might get multiple occurences of the same IP for various users, assuming those users are from the same company going out through the same proxy.
>
>Thank you (and Viv). For me it is important to log the IP of a user who submits within several seconds. Basically I am troubleshooting the following issue. Users submits duplicate orders by Submitting and then clicking on Back and Submitting again. They claim that they don't do it. And the only way I can prove to them (and to myself) is by logging every Submit with the IP and order number. So two submits within seconds with the consecutive order numbers and the same "IP" will show the trend.

You should probably protect yourself by not allowing that to happen in the first place - or at least make it difficult.
You could, for example, disable the submit button (and change the text to 'Please Wait' or somesuch) then, when the order is successfully submitted, clear the order details before re-enabling the button.