That's fixed with that upload: gdm (2.17.6-0ubuntu2) feisty; urgency=low . * debian/rules: - build with --enable-ipv6=yes ** Changed in: gdm (Ubuntu) Status: Confirmed => Fix Released -- XDMCP not working in ipv6, gdm should be compiled with --enable-ipv6=yes https://launchpad.net/bugs/75254