Anontools lists a number of tools to help investigate a user IP. It is used in MediaWiki:Anontalkpagetext and MediaWiki:Sp-contributions-footer-anon to link to these external sources with the user's IP as a parameter. Because it is used exclusively on MediaWiki pages, the template is fully protected.
This template was originally copied from Wikipedia.
Takes the user IP address as a parameter. Like this:
If you follow those links you will find out that the IP address used in this example is for a server in Wikimedia's Amsterdam cluster in the Netherlands.