http://drupal.org/project/globalredirect

drush dl globalredirect

Global redirect makes sure that when people visit a page on your site, they see your latest beautiful alias, not the Drupalish internal path or your second-to-last alias.

For instance, even if someone links to node/23 directly, they will be redirected to the aliased version, point/official-release-drupal-2-0

(Go to the module's project page for a 7 step description.)

This is great module for lazy people. All we have to do is enable it, and it starts doing its work.

There is a configuration page but the defaults will work fine for you in almost all cases.

SEO