If you are using a proxy with basic authentication (not NTLM), you will have to configure it for Bundler and Vagrant.
From your Windows host command line do
SET HTTP_PROXY=http://_XXX.XXX.XXX.XXX_:_port_
SET HTTPS_PROXY=ttp://_XXX.XXX.XXX.XXX_:_port_
SET HTTP_PROXY_USER=_proxyuser_
SET HTTPS_PROXY_USER=_proxyuser_
SET HTTP_PROXY_PASS=_userpasswd_
SET HTTPS_PROXY_PASS=_userpasswd_
Or from your Linux host command line do
export HTTP_PROXY=http://_XXX.XXX.XXX.XXX_:_port_
export HTTPS_PROXY=ttp://_XXX.XXX.XXX.XXX_:_port_
export HTTP_PROXY_USER=_proxyuser_
export HTTPS_PROXY_USER=_proxyuser_
export HTTP_PROXY_PASS=_userpasswd_
export HTTPS_PROXY_PASS=_userpasswd_
From the command line vagrant plugin install vagrant-proxyconf-1.5.2.gem
Last, edit Vagrantfile and change config.proxy.http, config.proxy.https and config.proxy.no_proxy values to the right IP and port and user/password.