The FIT Server automatically detects a sitemap.xml via the http://www.sitemaps.org/schemas/sitemap/0.9 namespace and rewrites the URLs defined in the <loc> elements to frontend URLs.
URLs already pointing to the FIT server and URLs that cannot be rewritten (e.g., because they are not allowed by the ACLs) remain untouched.
dump action can be used to prevent rewriting an entire sitemap.xml.<loc> element you can set the ai-rewrite attribute to false with an xslt or a set-attributes action.