Setting up browserSync + vagrant?

Question

gulp.js

I have a local project running in vagrant, I compile it using gulp. How to properly configure ports in vagrant and browsersync.
I tried that, it gives an error.

var gulp = require('gulp'),
      browserSync = require("browser-sync"),
      reload = browserSync.reload;

var config = {
    server: {
        baseDir: "./build"
    },
    proxy: {
        port: 2000
                }
};

...

Vagrant.configure("2") do |config|

    config.vm.box = "scotch"
    config.vm.network "private_network", ip: "192.168.33.10"
    config.vm.synced_folder "../../projects_vagrant/", "/home/vagrant/projects_vagrant", :mount_options => ["dmode=777", "fmode=666"]
    
end