3 level navigation in Sharepoint

I have the OOTB top navigation bar in Sharepoint 2010.

I want to create multi-level navigation in top navigation bar. How can I do this?

On one site, I read that opening the site master page in SP Designer and changing the "MaximumDynamicDisplayLevel" to 3 will do the changes, but it is not working.

I don't want to create any custom sitemap. How can I do this OOTB?