How to Install & Connect OpenOPN Client on Debian

A client is used to connect to remote openvpn server. This tutorial will help you to install OpenVPN packages for client on Debian system. Also connect to remote openvpn server via command line.

Before we begin

We assume you already have:

• A running Debian system with sudo privileged account access.
• OpenVPN server must be running on the remote system.
• Obtain an OpenVPN client configuration from remote host administrator.

Step 1 – Installing OpenVPN Client

The OpenVPN packages are available under the default Debian repositories. Open a terminal on your Debian system, and update the Apt cache on your system. After that install OpenVPN package.

Open a terminal and execute commands to install openvpn client on Debian:

sudo apt update 
sudo apt install openvpn -y 

Step 2 – Connect to OpenVPN Server

Copy the openvpn client configuration file on your Debian machine. You can use –config command line parameter to provide configuration file. The command will read all the required details for making a vpn from this file. Let’s execute the following command to connect to the openvpn server:

openvpn --config client.ovpn

You should see the following output:

Thu Sep 10 12:04:18 2020 TCP/UDP: Preserving recently used remote address: [AF_INET]69.87.218.145:1194
Thu Sep 10 12:04:18 2020 Socket Buffers: R=[212992->212992] S=[212992->212992]
Thu Sep 10 12:04:18 2020 UDP link local: (not bound)
Thu Sep 10 12:04:18 2020 UDP link remote: [AF_INET]69.87.218.145:1194
Thu Sep 10 12:04:18 2020 TLS: Initial packet from [AF_INET]69.87.218.145:1194, sid=6d27e1cb 524bd8cd
Thu Sep 10 12:04:18 2020 VERIFY OK: depth=1, CN=Easy-RSA CA
Thu Sep 10 12:04:18 2020 VERIFY OK: depth=0, CN=tecadmin-server
Thu Sep 10 12:04:18 2020 Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, 2048 bit RSA
Thu Sep 10 12:04:18 2020 [tecadmin-server] Peer Connection Initiated with [AF_INET]69.87.218.145:1194
Thu Sep 10 12:04:19 2020 SENT CONTROL [tecadmin-server]: 'PUSH_REQUEST' (status=1)
Thu Sep 10 12:04:19 2020 PUSH: Received control message: 'PUSH_REPLY,redirect-gateway def1,dhcp-option DNS 208.67.222.222,dhcp-option DNS 208.67.220.220,route 10.8.0.1,topology net30,ping 20,ping-restart 60,ifconfig 10.8.0.6 10.8.0.5,peer-id 0,cipher AES-256-GCM'
Thu Sep 10 12:04:19 2020 OPTIONS IMPORT: timers and/or timeouts modified
Thu Sep 10 12:04:19 2020 OPTIONS IMPORT: --ifconfig/up options modified
Thu Sep 10 12:04:19 2020 OPTIONS IMPORT: route options modified

Step 3 – Verify Connection

Once the connection established successfully, A new IP will be assigned on tun0 interface by the OpenVPN server. . You can check it with the following command:

ip a show tun0 

Output:

4: tun0:  mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 100
    link/none 
    inet 10.8.0.6 peer 10.8.0.5/32 scope global tun0
       valid_lft forever preferred_lft forever
    inet6 fe80::7226:57b1:f101:313b/64 scope link stable-privacy 
       valid_lft forever preferred_lft forever

You can also check the OpenVPN server log to verify the connection status:

tail -f /var/log/openvpn.log 

You should see the following output:

Thu Sep 10 12:04:18 2020 45.58.34.83:37445 Control Channel: TLSv1.3, cipher TLSv1.3 TLS_AES_256_GCM_SHA384, 2048 bit RSA
Thu Sep 10 12:04:18 2020 45.58.34.83:37445 [client] Peer Connection Initiated with [AF_INET]45.58.34.83:37445
Thu Sep 10 12:04:18 2020 client/45.58.34.83:37445 MULTI_sva: pool returned IPv4=10.8.0.6, IPv6=(Not enabled)
Thu Sep 10 12:04:18 2020 client/45.58.34.83:37445 MULTI: Learn: 10.8.0.6 -> client/45.58.34.83:37445
Thu Sep 10 12:04:18 2020 client/45.58.34.83:37445 MULTI: primary virtual IP for client/45.58.34.83:37445: 10.8.0.6
Thu Sep 10 12:04:19 2020 client/45.58.34.83:37445 PUSH: Received control message: 'PUSH_REQUEST'
Thu Sep 10 12:04:19 2020 client/45.58.34.83:37445 SENT CONTROL [client]: 'PUSH_REPLY,redirect-gateway def1,dhcp-option DNS 208.67.222.222,dhcp-option DNS 208.67.220.220,route 10.8.0.1,topology net30,ping 20,ping-restart 60,ifconfig 10.8.0.6 10.8.0.5,peer-id 0,cipher AES-256-GCM' (status=1)
Thu Sep 10 12:04:19 2020 client/45.58.34.83:37445 Data Channel: using negotiated cipher 'AES-256-GCM'
Thu Sep 10 12:04:19 2020 client/45.58.34.83:37445 Outgoing Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key
Thu Sep 10 12:04:19 2020 client/45.58.34.83:37445 Incoming Data Channel: Cipher 'AES-256-GCM' initialized with 256 bit key

Conclusion

Your Debian system is connected to the remote server over virtual private network. You can access the systems of remote network over local network.