[Solution] Vagrant can't mount shared folder in VirtualBox in Windows 8.1 OS!

                                    So to fix this problem all you need to do is install a plugin vagrant-vbguest using vagrant and the problem will be fixed. If you face troubles will installing vagrant-vbguest then go to this LINK=>[Solution of Vagrant plugin installation failure problem] and then just run the following command in command prompt as shown in the pic below.

after installation halt the vagrant using command vagrant halt and then run vagrant up and after that shared folder will mount in both windows and linux, fixed!