OpenVPN - ArchWiki

# OpenVPN

This article or section needs expansion.

Reason: (at least) add support for IPv6 and L2 Ethernet bridging (Discuss)

This article describes a basic installation and configuration of OpenVPN, suitable for private and small business use. For more detailed information, please see the OpenVPN 2.3 man page and the OpenVPN documentation.

OpenVPN is a robust and highly flexible VPN daemon. OpenVPN supports SSL/TLS security, Ethernet bridging, TCP or UDP tunnel transport through proxies or NAT, support for dynamic IP addresses and DHCP, scalability to hundreds or thousands of users, and portability to most major OS platforms.

OpenVPN is tightly bound to the OpenSSL library, and derives much of its crypto capabilities from it.

OpenVPN supports conventional encryption using a pre-shared secret key (Static Key mode) or public key security (SSL/TLS mode) using client & server certificates. OpenVPN also supports unencrypted TCP/UDP tunnels.

OpenVPN is designed to work with the TUN/TAP virtual networking interface that exists on most platforms.

Overall, OpenVPN aims to offer many of the key features of IPSec but with a relatively lightweight footprint.

OpenVPN was written by James Yonan and is published under the GNU General Public License (GPL).

## Install OpenVPN

Install openvpn from the official repositories.

Note: The software contained in this package supports both server and client mode, so install it on all machines that need to create VPN connections.

## Configure the system for TUN/TAP support

OpenVPN requires TUN/TAP support. Make sure to load at boot the `tun` module.

Read Kernel modules for more information.

The default kernel is already properly configured, but if you use another kernel make sure to enable the TUN/TAP module. If `$ zgrep CONFIG_TUN /proc/config.gz` returns `CONFIG_TUN=n`, make the following change to the kernel config file and rebuild the kernel.

    Kernel config file

     Device Drivers
      --> Network device support
        [M] Universal TUN/TAP device driver support

## Connect to a VPN provided by a third party

To connect to a VPN provided by a third party, most of the following can most likely be ignored. Use the certificates and instructions given by your provider, for instance see: Airvpn.

Note: To connect to servers of the most VPN providers that offer free service, one can plainly use PPTP server since most offers only this protocol.

## Create a Public Key Infrastructure (PKI) from scratch

If you are setting up OpenVPN from scratch, you will need to create a Public Key Infrastructure (PKI).

Create the needed certificates and keys by following: Create a Public Key Infrastructure Using the easy-rsa Scripts.

The final step of the key creation process is to copy the files needed to the correct machines through a secure channel.

Note: The rest of this article assumes that the keys and certificates are placed in `/etc/openvpn`.

The public ca.crt certificate is needed on all servers and clients. The private ca.key key is secret and only needed on the key generating machine.

A server needs server.crt, dh2048.pem (public), server.key, and ta.key (private).

A client needs client.crt (public), client.key, and ta.key (private).

## A basic L3 IP routing configuration

Note: Unless otherwise explicitly stated, the rest of this article assumes this basic configuration.

OpenVPN is an extremely versatile piece of software and many configurations are possible, in fact machines can be both "servers" and "clients", blurring the distinction between server and client.

What really distinguishes a server from a client (apart from the type of certificate used) is the configuration file itself. The OpenVPN daemon start-up script reads all the .conf configuration files it finds in `/etc/openvpn` on start-up and acts accordingly. If it finds more than one configuration file, it will start one OpenVPN process per configuration file.

This article explains how to set up a server named elmer and a client that connects to it named bugs. More servers and clients can easily be added by creating more key/certificate pairs and adding more server and client configuration files.

The OpenVPN package comes with a collection of example configuration files for different purposes. The sample server and client configuration files make an ideal starting point for a basic OpenVPN setup with the following features:

- Uses Public Key Infrastructure (PKI) for authentication.
- Creates a VPN using a virtual TUN network interface (OSI L3 IP routing).
- Listens for client connections on UDP port 1194 (OpenVPN's official IANA port number).
- Distributes virtual addresses to connecting clients from the 10.8.0.0/24 subnet.

For more advanced configurations, please see the official OpenVPN 2.2 man page and the OpenVPN documentation.

### The server configuration file

Copy the example server configuration file to `/etc/openvpn/server.conf`:

    # cp /usr/share/openvpn/examples/server.conf /etc/openvpn/server.conf

Edit the following:

- The `ca`, `cert`, `key`, and `dh` parameters to reflect the path and names of the keys and certificates. Specifying the paths will allow you to run the OpenVPN executable from any directory for testing purposes.
- Enable the SSL/TLS HMAC handshake protection. Note the use of the parameter 0 for a server.
- It is recommended to run OpenVPN with reduced privileges once it has initialized. Do this by uncommenting the `user` and `group` directives.

    /etc/openvpn/server.conf

    ca /etc/openvpn/ca.crt
    cert /etc/openvpn/elmer.crt
    key /etc/openvpn/elmer.key

    dh /etc/openvpn/dh2048.pem
    .
    .
    tls-auth /etc/openvpn/ta.key 0
    .
    .
    user nobody
    group nobody

Note: Note that if the server is behind a firewall or a NAT translating router, you will have to forward the OpenVPN UDP port (1194) to the server.

### The client configuration file

Copy the example client configuration file to `/etc/openvpn/client.conf`:

    # cp /usr/share/openvpn/examples/client.conf /etc/openvpn/client.conf

Edit the following:

- The `remote` directive to reflect either the server's Fully Qualified Domain Name, hostname (as known to the client), or its IP address.
- Uncomment the `user` and `group` directives to drop privileges.
- The `ca`, `cert`, and `key` parameters to reflect the path and names of the keys and certificates.
- Enable the SSL/TLS HMAC handshake protection. Note the use of the parameter 1 for a client.

    /etc/openvpn/client.conf

    remote elmer.acmecorp.org 1194
    .
    .
    user nobody
    group nobody
    .
    .
    ca /etc/openvpn/ca.crt
    cert /etc/openvpn/bugs.crt
    key /etc/openvpn/bugs.key
    .
    .
    tls-auth /etc/openvpn/ta.key 1

### Testing the OpenVPN configuration

Run `# openvpn /etc/openvpn/server.conf` on the server, and `# openvpn /etc/openvpn/client.conf` on the client. You should see something similar to this:

    # openvpn /etc/openvpn/server.conf

    Wed Dec 28 14:41:26 2011 OpenVPN 2.2.1 x86_64-unknown-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
    Wed Dec 28 14:41:26 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
    Wed Dec 28 14:41:26 2011 Diffie-Hellman initialized with 2048 bit key
    .
    .
    Wed Dec 28 14:41:54 2011 bugs/95.126.136.73:48904 MULTI: primary virtual IP for bugs/95.126.136.73:48904: 10.8.0.6
    Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 PUSH: Received control message: 'PUSH_REQUEST'
    Wed Dec 28 14:41:57 2011 bugs/95.126.136.73:48904 SENT CONTROL [bugs]: 'PUSH_REPLY,route 10.8.0.1,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5' (status=1)

    # openvpn /etc/openvpn/client.conf

    Wed Dec 28 14:41:50 2011 OpenVPN 2.2.1 i686-pc-linux-gnu [SSL] [LZO2] [EPOLL] [eurephia] built on Aug 13 2011
    Wed Dec 28 14:41:50 2011 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
    Wed Dec 28 14:41:50 2011 LZO compression initialized
    .
    .
    Wed Dec 28 14:41:57 2011 GID set to nobody
    Wed Dec 28 14:41:57 2011 UID set to nobody
    Wed Dec 28 14:41:57 2011 Initialization Sequence Completed

On the server, find the IP address assigned to the tunX device:

    # ip addr show

    .
    .
    40: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
        link/none
        inet 10.8.0.1 peer 10.8.0.2/32 scope global tun0

Here we see that the server end of the tunnel has been given the IP address 10.8.0.1.

Do the same on the client:

    # ip addr show

    .
    .
    37: tun0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 100
        link/none
        inet 10.8.0.6 peer 10.8.0.5/32 scope global tun0

And the client side has been given the IP address 10.8.0.6.

Now try pinging the interfaces.

On the server:

    # ping -c3 10.8.0.6

    PING 10.8.0.6 (10.8.0.6) 56(84) bytes of data.
    64 bytes from 10.8.0.6: icmp_req=1 ttl=64 time=238 ms
    64 bytes from 10.8.0.6: icmp_req=2 ttl=64 time=237 ms
    64 bytes from 10.8.0.6: icmp_req=3 ttl=64 time=205 ms

    --- 10.8.0.6 ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2002ms
    rtt min/avg/max/mdev = 205.862/227.266/238.788/15.160 ms

On the client:

    # ping -c3 10.8.0.1

    PING 10.8.0.1 (10.8.0.1) 56(84) bytes of data.
    64 bytes from 10.8.0.1: icmp_req=1 ttl=64 time=158 ms
    64 bytes from 10.8.0.1: icmp_req=2 ttl=64 time=158 ms
    64 bytes from 10.8.0.1: icmp_req=3 ttl=64 time=157 ms

    --- 10.8.0.1 ping statistics ---
    3 packets transmitted, 3 received, 0% packet loss, time 2001ms
    rtt min/avg/max/mdev = 157.426/158.278/158.940/0.711 ms

You now have a working OpenVPN installation, and your client (bugs) will be able to use services on the server (elmer), and vice versa.

Note: If using a firewall, make sure that IP packets on the TUN device are not blocked.

### Configure the MTU with Fragment and MSS

Note: If you do not configure MTU, then you will notice that small packets like ping and DNS will work, however web browsing will not work.

Now it is time to configure the maximum segment size (MSS). In order to do this we need to discover what is the smallest MTU along the path between the client and server. In order to do this you can ping the server and disable fragmentation. Then specify the max packet size.

    # ping -c5 -M do -s 1500 elmer.acmecorp.org

    PING elmer.acmecorp.org (99.88.77.66) 1500(1528) bytes of data.
    From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
    From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
    From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
    From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)
    From 1.2.3.4 (99.88.77.66) icmp_seq=1 Frag needed and DF set (mtu = 576)

    --- core.myrelay.net ping statistics ---
    0 packets transmitted, 0 received, +5 errors

We received an ICMP message telling us the MTU is 576 bytes. The means we need to fragment the UDP packets smaller then 576 bytes to allow for some UDP overhead.

    # ping -c5 -M do -s 548 elmer.acmecorp.org

    PING elmer.acmecorp.org (99.88.77.66) 548(576) bytes of data.
    556 bytes from 99.88.77.66: icmp_seq=1 ttl=48 time=206 ms
    556 bytes from 99.88.77.66: icmp_seq=2 ttl=48 time=224 ms
    556 bytes from 99.88.77.66: icmp_seq=3 ttl=48 time=206 ms
    556 bytes from 99.88.77.66: icmp_seq=4 ttl=48 time=207 ms
    556 bytes from 99.88.77.66: icmp_seq=5 ttl=48 time=208 ms

    --- myrelay.net ping statistics ---
    5 packets transmitted, 5 received, 0% packet loss, time 4001ms
    rtt min/avg/max/mdev = 206.027/210.603/224.158/6.832 ms

After some trial and error..., we discover that we need to fragment packets on 548 bytes. In order to do this we specify this fragment size in the configuration and instruct OpenVPN to fix the Maximum Segment Size (MSS).

    /etc/openvpn/client.conf

    remote elmer.acmecorp.org 1194
    .
    .
    fragment 548
    mssfix
    .
    .
    user nobody
    group nobody
    .
    .
    ca /etc/openvpn/ca.crt
    cert /etc/openvpn/bugs.crt
    key /etc/openvpn/bugs.key
    .
    .
    tls-auth /etc/openvpn/ta.key 1

Note: The following will add about 3 minutes to OpenVPN start time. It is advisable to configure the fragment size unless your client is a laptop that will be connecting over many different networks and the bottle neck is on the client side.

You can also allow OpenVPN to do this for you by having OpenVPN do the ping testing every time the client connects to the VPN. Be patient, since your client may not inform you about the test being run and the connection may appear as nonfunctional until finished.

    /etc/openvpn/client.conf

    remote elmer.acmecorp.org 1194
    .
    .
    mtu-test
    .
    .
    user nobody
    group nobody
    .
    .
    ca /etc/openvpn/ca.crt
    cert /etc/openvpn/bugs.crt
    key /etc/openvpn/bugs.key
    .
    .
    tls-auth /etc/openvpn/ta.key 1

### IPv6

In order to connect to a server which is only available with IPv6 (for example with DS Lite), you have to change

    /etc/openvpn/server.conf and /etc/openvpn/client.conf

    proto udp

to

    /etc/openvpn/server.conf and /etc/openvpn/client.conf

    proto udp6

in both server.conf and client.conf (See OpenVPN Wiki)

## Starting OpenVPN

### Manual startup

To troubleshoot a VPN connection, start the daemon manually with `openvpn /etc/openvpn/client.conf` as root.

### systemd service configuration

To start OpenVPN automatically at system boot, enable `openvpn@<configuration>.service`.

For example, if the configuration file is `/etc/openvpn/client.conf`, the service name is `openvpn@client.service`.

### Letting NetworkManager start a connection

On a client you might not always need to run a VPN tunnel and/or only want to establish it for a specific NetworkManager connection. This can be done by adding a script to `/etc/NetworkManager/dispatcher.d/`. In the following example "Provider" is the name of the NetworkManager connection:

    /etc/NetworkManager/dispatcher.d/10-openvpn

    #!/bin/bash

    case "$2" in
      up)
        if [ "$CONNECTION_ID" == "Provider" ]; then
          systemctl start openvpn@client
        fi
      ;;
      down)
        systemctl stop openvpn@client
      ;;
    esac

See NetworkManager#Network services with NetworkManager dispatcher for more details.

### OpenVPN not restarting after suspend

If you put your system to sleep, on resume openvpn doesn't restart, which results in broken connectivity.

    /usr/lib/systemd/system-sleep/vpn.sh

    #!/bin/sh
    if [ "$1" == "pre" ]
    then
      killall openvpn
    fi

Make it executable `chmod a+x /usr/lib/systemd/system-sleep/vpn.sh`

    /etc/systemd/system/openvpn@.service.d/restart.conf

    [Service]
    Restart=always

## L3 IPv4 routing

This section describes how to connect client/server LANs to each other using L3 IPv4 routing.

### Prerequisites for routing a LAN

#### IPv4 forwarding

For a host to be able to forward IPv4 packets between the LAN and VPN, it must be able to forward the packets between its NIC and its tun/tap device.

Edit or create `etc/sysctl.d/99-sysctl.conf` to permanently enable IPv4 packet forwarding (takes effect at the next boot):

    /etc/sysctl.d/99-sysctl.conf

    # Enable packet forwarding
    net.ipv4.ip_forward=1

Tip: To temporarily enable without rebooting: `# echo 1 > /proc/sys/net/ipv4/ip_forward`

#### Routing tables

The factual accuracy of this article or section is disputed.

Reason: Investigate if a routing protocol like RIP, QUAGGA, BIRD, etc can be used (Discuss)

By default, all IP packets on a LAN addressed to a different subnet get sent to the default gateway. If the LAN/VPN gateway is also the default gateway, there is no problem and the packets get properly forwarded. If not, the gateway has no way of knowing where to send the packets. There are a couple of solutions to this problem.

- Add a static route to the default gateway routing the VPN subnet to the LAN/VPN gateway's IP address.
- Add a static route on each host on the LAN that needs to send IP packets back to the VPN.
- Use iptables' NAT feature on the LAN/VPN gateway to masquerade the incoming VPN IP packets.

### Connect the server LAN to a client

The server is on a LAN using the 10.66.0.0/24 subnet. To inform the client about the available subnet, add a push directive to the server configuration file:

    /etc/openvpn/server.conf

    push "route 10.66.0.0 255.255.255.0"

Note: To route more LANs from the server to the client, add more push directives to the server configuration file, but keep in mind that the server side LANs will need to know how to route to the client.

### Connect the client LAN to a server

Prerequisites:

- Any subnets used on the client side, must be unique and not in use on the server or by any other client. In this example we will use 192.168.4.0/24 for the clients LAN.
- Each client's certificate has a unique Common Name, in this case bugs.
- The server may not use the duplicate-cn directive in its config file.

Create a client configuration directory on the server. It will be searched for a file named the same as the client's common name, and the directives will be applied to the client when it connects.

    # mkdir -p /etc/openvpn/ccd

Create a file in the client configuration directory called bugs, containing the `iroute 192.168.4.0 255.255.255.0` directive. It tells the server what subnet should be routed to the client:

    /etc/openvpn/ccd/bugs

    iroute 192.168.4.0 255.255.255.0

Add the client-config-dir and the `route 192.168.4.0 255.255.255.0` directive to the server configuration file. It tells the server what subnet should be routed from the tun device to the server LAN:

    /etc/openvpn/server.conf

    client-config-dir ccd
    route 192.168.4.0 255.255.255.0

Note: To route more LANs from the client to the server, add more iroute and route directives to the appropriate configuration files, but keep in mind that the client side LANs will need to know how to route to the server.

### Connect both the client and server LANs

Combine the two previous sections:

    /etc/openvpn/server.conf

    push "route 10.66.0.0 255.255.255.0"
    .
    .
    client-config-dir ccd
    route 192.168.4.0 255.255.255.0

    /etc/openvpn/ccd/bugs

    iroute 192.168.4.0 255.255.255.0

Note: Remember to make sure that all the LANs or the needed hosts can route to all the destinations.

### Connect clients and client LANs

By default clients will not see each other. To allow IP packets to flow between clients and/or client LANs, add a client-to-client directive to the server configuration file:

    /etc/openvpn/server.conf

    client-to-client

In order for another client or client LAN to see a specific client LAN, you will need to add a push directive for each client subnet to the server configuration file (this will make the server announce the available subnet(s) to other clients):

    /etc/openvpn/server.conf

    client-to-client
    push "route 192.168.4.0 255.255.255.0"
    push "route 192.168.5.0 255.255.255.0"
    .
    .

Note: As always, make sure that the routing is properly configured.

## L2 Ethernet bridging

This article or section needs expansion.

Reason: Please add a well thought out section on L2 bridging. (Discuss)

For now see: OpenVPN Bridge

## Contributions that do not yet fit into the main article

The factual accuracy of this article or section is disputed.

Reason: Not quite sure where this fits into the main article yet (Discuss)

### Routing client traffic through the server

Append the following to your server's openvpn.conf configuration file:

    push "redirect-gateway def1"
    push "dhcp-option DNS 192.168.1.1"

Change "192.168.1.1" to your preferred DNS IP address.

If you have problems with non responsive DNS after connecting to server, install BIND as simple DNS forwarder and push the IP address of the OpenVPN server as DNS to clients.

#### Configure ufw for routing

Configure your ufw settings to enable routing traffic from clients through server.

You must change default forward policy as in #IPv4 forwarding.

And then configure ufw in `/etc/default/ufw`:

    /etc/default/ufw

    DEFAULT_FORWARD_POLICY="ACCEPT"

Now change `/etc/ufw/before.rules`, and add the following code after the header and before the "*filter" line. Don't forget to change the IP/subnet mask to match the one in `/etc/openvpn/server.conf`.

    /etc/ufw/before.rules

    # NAT (Network Address Translation) table rules
    *nat
    :POSTROUTING ACCEPT [0:0]

    # Allow traffic from clients to enp1s0
    -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE

    # don't delete the "COMMIT" line or the NAT table rules above won't be processed
    COMMIT

Open OpenVPN port 1194:

    ufw allow 1194

#### Using iptables

Use an iptable for NAT forwarding:

    echo 1 > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE

If running Arch Linux in a OpenVZ VPS environment [1]:

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)

If all is well, make the changes permanent:

Edit `/etc/conf.d/iptables` and change IPTABLES_FORWARD=1

    # iptables-save > /etc/iptables/iptables.rules

### Configuring LDAP authorization

The factual accuracy of this article or section is disputed.

Reason: what does the following do, and is the package still supported? (Discuss)

You may also want to install openvpn-authldap-plugin, available in the AUR.

### Deprecated older wiki content

The factual accuracy of this article or section is disputed.

Reason: See how this older content can be fitted into the new article (Discuss)

#### Using PAM and passwords to authenticate

    port 1194
    proto udp
    mtu-test
    dev tap
    ca /etc/openvpn/easy-rsa/keys/ca.crt
    cert /etc/openvpn/easy-rsa/keys/<MYSERVER>.crt
    key /etc/openvpn/easy-rsa/keys/<MYSERVER>.key
    dh /etc/openvpn/easy-rsa/keys/dh2048.pem
    server 192.168.56.0 255.255.255.0
    ifconfig-pool-persist ipp.txt
    ;learn-address ./script
    client-to-client
    ;duplicate-cn
    keepalive 10 120
    ;tls-auth ta.key 0
    comp-lzo
    ;max-clients 100
    ;user nobody
    ;group nobody
    persist-key
    persist-tun
    status /var/log/openvpn-status.log
    verb 3
    client-cert-not-required
    username-as-common-name
    plugin /usr/lib/openvpn/plugins/openvpn-plugin-auth-pam.so login

#### Using certs to authenticate

    port 1194
    proto tcp
    dev tun0

    ca /etc/openvpn/easy-rsa/keys/ca.crt
    cert /etc/openvpn/easy-rsa/keys/<MYSERVER>.crt
    key /etc/openvpn/easy-rsa/keys/<MYSERVER>.key
    dh /etc/openvpn/easy-rsa/keys/dh2048.pem

    server 10.8.0.0 255.255.255.0
    ifconfig-pool-persist ipp.txt
    keepalive 10 120
    comp-lzo
    user nobody
    group nobody
    persist-key
    persist-tun
    status /var/log/openvpn-status.log
    verb 3

    log-append /var/log/openvpn
    status /tmp/vpn.status 10

#### Routing traffic through the server

Append the following to your server's openvpn.conf configuration file:

    push "dhcp-option DNS 192.168.1.1"
    push "redirect-gateway def1"

Change "192.168.1.1" to your external DNS IP address.

Use an iptable for NAT forwarding:

    echo 1 > /proc/sys/net/ipv4/ip_forward
    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o enp1s0 -j MASQUERADE

If running Arch Linux in a OpenVZ VPS environment [2]:

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o venet0 -j SNAT --to (venet0 ip)

If all is well, make the changes permanent:

Edit `/etc/conf.d/iptables` and change IPTABLES_FORWARD=1

    # iptables-save > /etc/iptables/iptables.rules

#### Setting up the client

The client-side .conf file

##### With password authentication

    client
    dev tap
    proto udp
    mtu-test
    remote <address> 1194
    resolv-retry infinite
    nobind
    persist-tun
    comp-lzo
    verb 3
    auth-user-pass passwd
    ca ca.crt

passwd file (referenced by auth-user-pass) must contain two lines:

- first line - username
- second - password

##### Certificates authentication

    client
    remote <MYSERVER> 1194
    dev tun0
    proto tcp
    resolv-retry infinite
    nobind
    persist-key
    persist-tun
    verb 2
    ca ca.crt
    cert client1.crt
    key client1.key
    comp-lzo

Copy three files from server to remote computer.

    ca.crt
    client1.crt
    client1.key

Install the tunnel/tap module:

    # modprobe tun

To have the tun module loaded automatically at boot, read Kernel_modules.

##### DNS

The DNS servers used by the system are defined in `/etc/resolv.conf`. Traditionally, this file is the responsibility of whichever program deals with connecting the system to the network (e.g. Wicd, NetworkManager, etc...) However, OpenVPN will need to modify this file if you want to be able to resolve names on the remote side. To achieve this in a sensible way, install openresolv, which makes it possible for more than one program to modify resolv.conf without stepping on each-other's toes. Before continuing, test openresolv by restarting your network connection and ensuring that resolv.conf states that it was generated by "resolvconf", and that your DNS resolution still works as before. You should not need to configure openresolv; it should be automatically detected and used by your network system.

Next, save the following script at `/etc/openvpn/update-resolv-conf.sh`: https://raw.githubusercontent.com/masterkorp/openvpn-update-resolv-conf/master/update-resolv-conf.sh

Remember to make the file executable with:

     $ chmod +x /etc/openvpn/update-resolv-conf.sh

Next, add the following lines to your OpenVPN client configuration file:

    script-security 2
    up /etc/openvpn/update-resolv-conf.sh
    down /etc/openvpn/update-resolv-conf.sh

Now, when your launch your OpenVPN connection, you should find that your resolv.conf file is updated accordingly, and also returns to normal when your close the connection.

Caveat: The script will fail to restore the original DNS settings if your OpenVPN client configuration is set-up to drop root privileges after connection. To avoid running OpenVPN as root you can add a locked-down user which only is allowed to use sudo on resolvconf. Then you have to change the `RESOLVCONF` variable in the script to `RESOLVCONF=/usr/bin/sudo /usr/bin/resolvconf` and the DNS restoration on disconnect should work with the generally dropped root privileges as well.

##### Webmin

webmin-plugin-openvpn is available in the AUR.

Note: You must add "openvpn" to the end of `/etc/webmin/webmin.acl`.

#### Connecting to the server

You need to start the service on the server

    systemctl start openvpn@server

To make it permanent:

    systemctl enable openvpn@server

On the client, in the home directory create a folder that will hold your OpenVPN client config files along with the .crt/.key files. Assuming your OpenVPN config folder is called .openvpn and your client config file is vpn1.conf, to connect to the server issue the following command:

    # cd ~/.openvpn && openvpn vpn1.conf

## Troubleshooting

### Resolve issues

If you are having resolve issues when starting your profile:

    # journalctl _SYSTEMD_UNIT=openvpn@profile.service

    RESOLVE: Cannot resolve host address: example.com: Name or service not known

The factual accuracy of this article or section is disputed.

Reason: Ordering "After=network.target" does not work universally. See network.target. Further, not the original unit in `/usr/lib` should be modified but a copy, cross-referencing Systemd#Editing provided unit files. (Discuss)

Then, only if your network setup can be started before OpenVPN, you should force OpenVPN to wait for the network by adding `Requires=network.target` and `After=network.target` to the OpenVPN systemd service file:

    /usr/lib/systemd/system/openvpn@.service

    [Unit]
    Description=OpenVPN connection to %i
    Requires=network.target
    After=network.target
    ...

Don't forget to restart OpenVPN:

    # systemctl daemon-reload
    # systemctl restart openvpn@profile

## See Also

- VPNBook Ruby Script (Free OpenVPN)

Category:

- Virtual Private Network