Vagrant reverse port forwarding?

Question

When you run vagrant ssh, it's actually using this underlying command:

ssh -p 2222 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o LogLevel=ERROR -o IdentitiesOnly=yes -i ~/.vagrant.d/insecure_private_key [email protected]

SSH supports forwarding ports in the direction you want with the -R guestport:host:hostport option. So, if you wanted to connect to port 12345 on the guest and have it forwarded to localhost:80, you would use this command:

ssh -p 2222 -R 12345:localhost:80 -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o LogLevel=ERROR -o IdentitiesOnly=yes -i ~/.vagrant.d/insecure_private_key [email protected]

As Eero correctly comments, you can also use the command vagrant ssh -- -R 12345:localhost:80, which has the same effect in a much more concise command.

In the book Vagrant: Up and Running (Pub. date: June 12, 2013), written by the creator of Vagrant, he mentioned that it is not possible for guest machine to access services running on the host machine.

Instead of using Forwarded Ports, you could set up a private network using Host-Only Networks.

• Pros of using Host-Only Networks over Forwarded Ports

  1. Guest machines may access the services running on host machine

     This feature would solve your problem.

  2. Guest machines may access the services running on other guest machine

     This feature is very useful to separate services onto multiple machines to more accurately mimic a production environment.

  3. Secure

     Outside machines have no ways to access the services running on the guest machines

  4. Less work

     No need to configure every single Forwarded Port

---

• How to configure Host-Only Networks

  config.vm.network :"hostonly", "192.168.0.0" # Vagrant Version #1

  config.vm.network :private_network, ip: "192.168.0.0" # Vagrant Version #2

  Having this line in your Vagrantfile will instruct vagrant to create a private network that has a static IP address: 192.168.0.0

  The IP address of the host is always the same IP address but with the final octet as a 1. In the preceding example, the host machine would have the IP address 192.168.0.1.

You can access ports on the host machine through the default gateway inside the guest OS. (Which typically has an IP of 10.0.2.2.)

For example, if you have a webserver running on port 8000 on your host machine...

echo 'Hello, guest!' > hello
python -m SimpleHTTPServer 8000

You can access it from inside the Vagrant VM at 10.0.2.2:8000 (provided 10.0.2.2 is the ip of the guest's default gateway):

vagrant ssh
curl http://10.0.2.2:8000/hello # Outputs: Hello, guest!

To find the IP of the default gateway inside the guest OS, run netstat -rn (or ipconfig on a Windows guest) and look for the row with a destination IP of 0.0.0.0 (or the field labeled "Default Gateway" on Windows):

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         10.0.2.2        0.0.0.0         UG        0 0          0 eth0
10.0.2.0        0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.33.0    0.0.0.0         255.255.255.0   U         0 0          0 eth1

You can extract this IP programmatically with netstat -rn | grep "^0.0.0.0 " | tr -s ' ' | cut -d " " -f2.

_{Sources: How to connect with host PostgreSQL from vagrant virtualbox machine; Connect to the host machine from a VirtualBox guest OS?}

Add following to your ~/.ssh/config on the host machine:

Host 127.0.0.1
RemoteForward 52698 127.0.0.1:52698

It lets you access a service on host machine port 52698 from Vagrant, as long as you logged in via vagrant ssh.

You can confirm it works by running netstat -lt on vagrant VM and taking a note on the following lines:

tcp      0    0 localhost:52698         *:*                 LISTEN
tcp6     0    0 ip6-localhost:52698     [::]:*              LISTEN