1. The content of this article should be valid
     for Linux 2.6.38, 2.6.39, 3.0 and 3.1. There are some
     clues for Linux 2.6.35, 2.6.36 and 2.6.37 as well
     as for Linux 3.2, 3.3, 3.4 and 3.5. Starting from
     Linux 3.6, the whole route cache has been removed.