This tool is similar with reverse ip checker tool but this tool you check websites by NS .Enter the url of the Name server and it will show you all domain hosted on that DNS. A website can have more than 2 DNS. This NS checker will show all websites using that specific NS.
Using this tool is very easy, enter the NS url in the input box and click on the Check Now button. After that you can view all websites list against that NS. It will also count the number of domain hosted on it.