Step 1: Initialize OpenVPN using Docker

Table of Contents

• Step 1: Initialize OpenVPN using Docker

  • 6.1.1. Choosing a VPN port

  • 6.1.2. Set up the Docker Container

    • Verify the Installation

Objective: Create an OpenVPN Docker container using the default configuration.

6.1.1. Choosing a VPN port

Before you begin, choose a UDP port (or ports) that you want to use for your OpenVPN connection. You might ask, why does a port matter?

Outgoing port restrictions

Some networks restrict ports to control outgoing traffic. For example, a network wants to prevent torrents (port ranges 6700-6999) or defend again viruses that use Window’s file sharing (135-139). A network might block the VPN port 1194 intentionally.

• Using a common port can by-pass that restriction.

Seeking to be anonymous

Using port 1194 announces to your ISP or network admin that you are using a VPN. You might want to hide that you are using a VPN.

• Using another port can help mask a VPN tunnel.

• It takes a sophisticated operation to detect a VPN.

---

1. Browse the List of TCP and UDP port numbers from Wikipedia.

2. Select a well-known UDP port that is likely to be open (DNS, NTP), that masks your usage (masquerade your data as a streaming video or game), or pick a port at random.

   Suggested UDP Ports

   UPD Port Number	Description
   22	Secure Shell (SSH)
   53	Domain Name System (DNS)
   123	Network Time Protocol (NTP)
   465
   554	Real Time Streaming Protocol (RTSP)
   943
   972
   995	Post Office Protocol 3 over TLS/SSL (POP3S)
   1935	Real Time Messaging Protocol (RTMP)
   1234	VLC media player default port for UDP/RTP stream
   10007	VoIP providers (ports 10000-20000)
   11211	Memcached
   3074	Xbox LIVE
   3748
   5005	Real-time Transport Protocol media data (RTP)
   5730
   8080
   17500	Dropbox LanSync Protocol (db-lsp)
   25575	Minecraft

3. Open the port in your firewall.

   • Typically, VPNs use UDP instead of TCP.

   • We can open a port on the firewall to accept UDP traffice only.

   • For example, this command open ports 123 using UDP. The firewall rejects TCP requests using port 123.

ufw allow 123/udp

6.1.2. Set up the Docker Container

Note

This page is based on @gurayy’s Set Up a VPN Server With Docker In 5 Minutes blog post.

• We will make some configuration changes.

1. Follow the Set Up a VPN Server With Docker In 5 Minutes guide

2. Note the following changes

   1. Replace $PWD with /root for all instances

      • $PWD returns or displays the current directory.

      • This path will become incorrect if the user is not in the home directory.

   2. Replace IP_ADDRESS:3000 with the IP address of your VPS.

   3. Replace the port (3000) with a port of your choice.

   4. Add the --name flag to the run command that starts the daemon process

Example of changes

Verify the Installation

At this point, you should have OpenVPN running in a Docker container and the configs files stored in ~/vpn-data.

Verify that:

1. the firewall accepts UDP connections on the specified port.

2. the Docker container is running.

   • You should see your running OpenVPN container with an exposed port mapped to 1194.

3. the configuration files are in directory ~/vpn-data.

   root@vps298933:~# ls -lh ~/vpn-data/
   total 20K
   drwxr-xr-x 2 root root 4.0K Apr 18 21:04 ccd
   -rw-r--r-- 1 root root  650 Apr 18 21:06 crl.pem
   -rw-r--r-- 1 root root  642 Apr 18 21:04 openvpn.conf
   -rw-r--r-- 1 root root  813 Apr 18 21:04 ovpn_env.sh
   drwx------ 6 root root 4.0K Apr 18 21:09 pki
   root@vps298933:~#
   

4. you have a file with an extension .ovpn in the root (~) directory.

5. Edit the .ovpn file using nano or another editor and verify that the IP address, port and protocol are correct.

The configuration might work on some systems, but there is a configuration error that prevents the client from communicating with the VPN server. Please continue to the next step to correct the invalid configuration.