You can generate reports for internal and external links, and there is an optional flag that allows you to exclude external links during site checking.
Normally, when Site checker is examining a page and finds a link that points to an external document, it will check to see if that external document exists. If the check external links option is disabled, external links will not be checked.
Using the "Verifying external links" option takes between 5 and 10 minutes to complete.