Subnet address in apache access log

view story

http://serverfault.com – I was inspecting my apache access logs(I use default combined log format) and I came a cross a wired entry - - [22/Oct/2012:18:15:20 +0200] "GET /some site resources HTTP/1.1" 404 514 "-" "facebookexternalhit/1.0 (+http://www.facebook.com/externalhit_uatext.php)" As u see, this query come from a facebook robot that extract objects from site when somebody post a link. What I find weird is the logged ip address : Does anybody know how is that possible ? (HowTos)