Boxes 3.12 can do bridged networking by default which is way better than usermode network (it can do icmp, it can communicate with the host, it can communicate with other machines in the host's network, etc etc). to enable bridged networking in Fedora, you need to install libvirt-daemon-config-network. gnome-boxes should require that so users will have the best boxes experience "out of the box".
Pushed a build in rawhide with this fixed. Thanks! Having said that, I think libvirt doesn't create the needed infra on installation of this package but only at boot so if user installs Boxes, they'll still not get this working out of the box. :(
This bug appears to have been reported against 'rawhide' during the Fedora 22 development cycle. Changing version to '22'. More information and reason for this action is here: https://fedoraproject.org/wiki/Fedora_Program_Management/HouseKeeping/Fedora22
Fedora 22 changed to end-of-life (EOL) status on 2016-07-19. Fedora 22 is no longer maintained, which means that it will not receive any further security or bug fix updates. As a result we are closing this bug. If you can reproduce this bug against a currently maintained version of Fedora please feel free to reopen this bug against that version. If you are unable to reopen this bug, please file a new report against the current release. If you experience problems, please add a comment to this bug. Thank you for reporting this bug and we are sorry it could not be fixed.
It may be worth noting this is actually fixed now in 3.22.1-2 (f25) and 3.20.3-1 (f24).