What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Yes it is possible to prevent users from submitting form multiple times from the same IP address.
You can take advantage of our "Unique Submission" feature to block multiple submissions from one system or one IP address by setting the "Check Cookies Only (Loose check)" or "Check Cookies & IP address (Strict Check)" respectively.
You may like to take a look at the following guide which should help you: http://www.jotform.com/help/64-How-to-Set-Unique-Submissions-on-a-Form
Hope this helps.
Do try ti out and get back to us if you have any questions.