Ever since I upgraded my virtualbox I was having issues with vagrant when I returned from standby. The pages I was trying to load kept going until they gave me a gateway timeout.
The following command seems to solve the virtualbox issue and will ensure your vagrant box will be running better then ever after a return from standby!
sudo launchctl load /Library/LaunchDaemons/org.virtualbox.startup.plist
Next up it’s best to startup vagrant using the provision command, which will force to startup all the services from scratch again.
vagrant up --provision