If you configure your network this way in the Vagrant file:
config.vm.network :forwarded_port, guest: 4000, host: 4000
And then serve files on that port. You will be able to hit it externally. Assuming you are running the vagrant box on a Mac it would be (machine).local:4000, for example I’m joe.local:4000
Quite convenient to be able to use an iPad and an iPhone as your preview monitors as you work on a responsive site, if you have livereload or equivalent going you don’t even need to touch them.