OpenVPN

Related articles
Linux_Containers/Using_VPNs
OpenVPN Checklist Guide
Easy-RSA
This article describes a basic installation and configuration of
OpenVPN
, suitable for private and small business use. For more detailed information, please see
openvpn(8)
and the
OpenVPN documentation
[
dead link
2025-11-17—HTTP 404]
. OpenVPN is a robust and highly flexible
VPN
daemon. It supports
SSL/TLS
security,
Ethernet bridging
,
TCP
or
UDP
tunnel transport
through
proxies
or
NAT
. Additionally it has 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. It supports conventional encryption using a
pre-shared secret key
(Static Key mode) or
public key security
(
SSL/TLS
mode) using client & server certificates. Additionally it supports unencrypted TCP/UDP tunnels.
OpenVPN is designed to work with the
TUN/TAP
virtual networking interface that exists on most platforms. Overall, it 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)
.
Installation
Install
the
openvpn
package, which provides both server and client mode.
There's also
openvpn3
AUR
client to connect to newer server.
Available frontends:
NetworkManager OpenVPN
— NetworkManager VPN plugin for OpenVPN.
https://wiki.gnome.org/Projects/NetworkManager/VPN
||
networkmanager-openvpn
QOpenVPN
— Simple OpenVPN GUI written in PyQt for systemd based distributions.
https://github.com/xmikos/qopenvpn
||
qopenvpn
eOVPN
— Application to connect, manage and update OpenVPN configurations. Written in GTK. Supports both OpenVPN 2 and OpenVPN 3 with
Data Channel Offload
https://github.com/jkotra/eOVPN
||
eovpn
AUR
Kernel configuration
OpenVPN requires TUN/TAP support, which is already configured in the default kernel. Users of custom kernel should make sure to enable the
tun
module (
CONFIG_TUN
) in
Device Drivers > Network device support > Network core driver support > Universal TUN/TAP device driver support
.
Read
Kernel module
for more information.
Connect to a VPN provided by a third party
To connect to a VPN service provided by a third party, most of the following can most likely be ignored, especially regarding server setup. Begin with
#The client configuration profile
and skip ahead to
#Starting OpenVPN
after that. One should use the provider certificates and instructions, see
Category:VPN providers
for examples that can be adapted to other providers.
OpenVPN client in Linux Containers
also has general applicable instructions, while it goes a step further by isolating an OpenVPN client process into a container.
Note
Most free VPN providers will (often only) offer
PPTP
, which is drastically easier to setup and configure, but
not secure
.
Create a Public Key Infrastructure (PKI) from scratch
When setting up an OpenVPN server, users need to create a
Public Key Infrastructure (PKI)
which is detailed in the
Easy-RSA
article.  Once the needed certificates, private keys, and associated files are created via following the steps in the separate article, one should have 5 files in
/etc/openvpn/server
at this point:
ca.crt
dh.pem
servername.crt
servername.key
ta.key
Alternatively, as of OpenVPN 2.4, one can use Easy-RSA to generate certificates and keys using elliptic curves. See the OpenVPN documentation for details.
A basic Layer-3 IP routing configuration
Note
Unless otherwise explicitly stated, the rest of this article assumes a basic Layer-3 IP routing configuration.
OpenVPN is an extremely versatile piece of software and many configurations are possible, in fact machines can be both servers and clients.
With the release of v2.4, server configurations are stored in
/etc/openvpn/server
and client configurations are stored in
/etc/openvpn/client
and each mode has its own respective systemd unit, namely,
openvpn-client@.service
and
openvpn-server@.service
.
Example configuration
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 Layer-3 IP routing).
Listens for client connections on UDP port 1194 (OpenVPN's official IANA port number
[1]
).
Distributes virtual addresses to connecting clients from the 10.8.0.0/24 subnet.
For more advanced configurations, please see the
openvpn(8)
man page and the
OpenVPN documentation
[
dead link
2025-11-17—HTTP 404]
.
The server configuration file
Note
Note that if the server is behind a firewall or a NAT translating router, the OpenVPN port must be forwarded on to the server.
Copy the example server configuration file
/usr/share/openvpn/examples/server.conf
to
/etc/openvpn/server/server.conf
.
Edit the file making a minimum of the following changes:
/etc/openvpn/server/server.conf
ca ca.crt
cert servername.crt
key servername.key
dh dh.pem

tls-crypt ta.key # Replaces
tls-auth ta.key 0
user nobody
group nobody
If TLS with elliptic curves is used, specify
dh none
and
ecdh-curve secp521r1
(or
ecdh-curve ed25519
). DH parameters file is not used when using elliptic curves. Starting from OpenVPN 2.4.8, it is required to specify the type of elliptic curves in server configuration. Otherwise the server would fail to recognize the curve type and possibly use an incompatible one, resulting in authentication errors.
Hardening the server
If security is a priority, additional configuration is recommended including: limiting the server to use a strong cipher/auth method and (optionally) limiting the set of enabled TLS ciphers to the newer ciphers. Starting from OpenVPN 2.4, the server and the client will automatically negotiate AES-256-GCM in TLS mode.
Add the following to
/etc/openvpn/server/server.conf
:
This article or section needs language, wiki syntax or style improvements. See
Help:Style
for reference.
Reason:
Usage instructions belong into the wiki text, not into code blocks. Avoid subjective terms like "bleeding edge security". (Discuss in
Talk:OpenVPN
)
Bleeding edge security:
/etc/openvpn/server/server.conf
cipher AES-256-GCM
auth SHA512
tls-version-min 1.3
#Uncomment  tls-cipher to limit possible negotiation options to the strongest ciphers, doing so it's no longer possible to generate certs with current easyrsa,
more information
#tls-cipher TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256
This article or section needs language, wiki syntax or style improvements. See
Help:Style
for reference.
Reason:
Compatibility options do not fit into a hardening section. (Discuss in
Talk:OpenVPN
)
Compatibility with most devices:
/etc/openvpn/server/server.conf
cipher AES-256-GCM
auth SHA512
tls-version-min 1.2
tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-128-GCM-SHA256:TLS-DHE-RSA-WITH-AES-256-CBC-SHA:TLS-DHE-RSA-WITH-CAMELLIA-256-CBC-SHA:TLS-DHE-RSA-WITH-AES-128-CBC-SHA:TLS-DHE-RSA-WITH-CAMELLIA-128-CBC-SHA
Note
The .ovpn client profile
must
contain a matching cipher and auth line to work properly (at least with the iOS and Android client).
Using
tls-cipher
incorrectly may cause difficulty with debugging connections and may not be necessary. See
OpenVPN’s community wiki
for more information.
Enabling compression
Enabling compression is not recommended by upstream; doing so opens to the server the so-called VORACLE attack vector.  See
this
article.
Deviating from the standard port and/or protocol
It is generally recommended to use OpenVPN over UDP, because
TCP over TCP is a bad idea
[2]
.
Some networks may disallow OpenVPN connections on the default port and/or protocol. One strategy to circumvent this is to mimic HTTPS traffic which is very likely unobstructed.
To do so, configure
/etc/openvpn/server/server.conf
as such:
/etc/openvpn/server/server.conf
port 443
proto tcp
Note
The .ovpn client profile
must
contain a matching port and proto line to work properly!
Running multiple instances of OpenVPN on different ports on the physical machine
One can have multiple, concurrent instances of OpenVPN running on the same box.  Each server needs to be defined in
/etc/openvpn/server/
as a separate .conf file.  At a minimum, the parallel servers need to be running on different ports.  A simple setup directs traffic connecting in to a separate IP pool.  More advanced setups are beyond the scope of this guide.
Consider this example, running 2 concurrent servers, one port 443/udp and another on port 80/tcp.
First modify
/etc/openvpn/server/server.conf
created as so:
/etc/openvpn/server/server.conf
port 443
proto udp
server 10.8.0.0 255.255.255.0
Now copy it and modify the copy to run on 80/tcp:
/etc/openvpn/server/server2.conf
port 80
proto tcp
server 10.8.1.0 255.255.255.0
Be sure to setup the corresponding entries in the firewall, see the relevant sections in
#Firewall configuration
.
The client configuration profile
Copy the example client configuration file
/usr/share/openvpn/examples/client.conf
to
/etc/openvpn/client/
.
This article or section is out of date.
Reason:
As of 2.5.0-3, "OpenVPN now uses a netlink interface for network configuration. The systemd units start the process with a dedicated unprivileged user 'openvpn', with extra capabilities(7). The configuration should no longer drop privileges, so remove 'user' and 'group' directives. Scripts that require elevated privileges may need a workaround." (Discuss in
Talk:OpenVPN
)
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 TLS HMAC handshake protection (
--tls-crypt
or
--tls-auth
).
/etc/openvpn/client/client.conf
client
remote elmer.acmecorp.org 1194

user nobody
group nobody
ca ca.crt
cert client.crt
key client.key

tls-crypt ta.key # Replaces
tls-auth ta.key 1
Run as unprivileged user
Using the options
user nobody
and
group nobody
in the configuration file makes
OpenVPN
drop its
root
privileges after establishing the connection. The downside is that upon VPN disconnect the daemon is unable to delete its set network routes again. If one wants to limit transmitting traffic without the VPN connection, then lingering routes may be considered beneficial. It can also happen, however, that the OpenVPN server pushes updates to routes at runtime of the tunnel. A client with dropped privileges will be unable to perform the update and exit with an error.
As it could seem to require manual action to manage the routes, the options
user nobody
and
group nobody
might seem undesirable. Depending on setup, however, there are different ways to handle these situations:
For errors of the unit, a simple way is to
edit
it and add a
Restart=on-failure
to the
[Service]
section. Though, this alone will not delete any obsoleted routes, so it may happen that the restarted tunnel is not routed properly.
The package contains the
/usr/lib/openvpn/plugins/openvpn-plugin-down-root.so
, which can be used to let
openvpn
fork a process with root privileges with the only task to execute a custom script when receiving a down signal from the main process, which is handling the tunnel with dropped privileges (see also its
README
).
The OpenVPN HowTo's linked below go further by creating a dedicated non-privileged user/group, instead of the already existing
nobody
. The advantage is that this avoids potential risks when sharing a user among daemons:
The
OpenVPN HowTo
explains another way how to create an unprivileged user mode and wrapper script to have the routes restored automatically.
It is possible to let OpenVPN start as a non-privileged user in the first place, without ever running as root, see
this OpenVPN wiki
(howto). The howto assumes the presence of System V init, rather than
Systemd
and does not cover the handling of
--up
/
--down
scripts - those should be handled the same way as the
ip
command, with additional attention to access rights.
It is also possible to run OpenVPN from within unprivileged podman container, see
this section of OpenVPN HowTo
Tip
#openvpn-unroot
describes a tool to automate above setup.
Converting certificates to encrypted .p12 format
Some software will only read VPN certificates that are stored in a password-encrypted .p12 file. These can be generated with the following command:
# openssl pkcs12 -export -inkey keys/bugs.key -in keys/bugs.crt -certfile keys/ca.crt -out keys/bugs.p12
Testing the OpenVPN configuration
Run
openvpn /etc/openvpn/server/server.conf
(as the root user) on the server, and
openvpn /etc/openvpn/client/client.conf
(as the root user) on the client.  Example output should be similar to the following:
# openvpn /etc/openvpn/server/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/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 14:41:57 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
Find the IP address
assigned to the tunX interface on the server, and
ping
it from the client.
Find the IP address
assigned to the tunX interface on the client, and
ping
it from the server.
Note
If using a firewall, make sure that IP packets on the TUN device are not blocked.
Configure the MTU with Fragment and MSS
If experiencing issues when using (remote) services over OpenVPN (e.g. web browsing,
DNS
,
NFS
), it may be needed to set a MTU value manually.
The following message may indicate the MTU value should be adjusted:
read UDPv4 [EMSGSIZE Path-MTU=1407]: Message too long (code=90)
In order to get the  maximum segment size (MSS), the client needs to discover the smallest MTU along the path to the server. In order to do this  ping the server and disable fragmentation, then specify the maximum packet size
[3]
:
# ping -M do -s 1500 -c 1 example.com
Decrease the 1500 value by 10 each time, until the ping succeeds.
Note
Clients that do not support the 'fragment' directive (e.g. OpenELEC,
iOS app
) are not able to connect to a server that uses the
fragment
directive. See
mtu-test
as alternative solution.
Update the client configuration to use the succeeded MTU value, e.g.:
/etc/openvpn/client/client.conf
remote example.com 1194

tun-mtu 1400 
mssfix 1360
OpenVPN may be instructed to test the MTU every time on client connect. Be patient, since the client may not inform about the test being run and the connection may appear as nonfunctional until finished.  The following will add about 3 minutes to OpenVPN start time. It is advisable to configure the fragment size unless a client will be connecting over many different networks and the bottle neck is not on the server side:
/etc/openvpn/client/client.conf
remote example.com 1194

mtu-test
IPv6
Connect to the server via IPv6
Starting from OpenVPN 2.4, OpenVPN will use
AF_INET
defined by the OS when just using
proto udp
or
proto tcp
, which in most cases will be IPv4 only. To use both IPv4 and IPv6, use
proto udp6
or
proto tcp6
. To enforce only IPv4-only, use
proto udp4
or
proto tcp4
. On older OpenVPN versions, one server instance can only support either IPv4 or IPv6.
Provide IPv6 inside the tunnel
In order to provide IPv6 inside the tunnel, have an IPv6 prefix routed to the OpenVPN server. Either set up a static route on the gateway (if a static block is assigned), or use a DHCPv6 client to get a prefix with DHCPv6 Prefix delegation (see
IPv6 Prefix delegation
for details). Also consider using a unique local address from the address block fc00::/7. Both methods have advantages and disadvantages:
Many ISPs only provide dynamically changing IPv6 prefixes. OpenVPN does not support prefix changes, so change the server.conf every time the prefix is changed (Maybe can be automated with a script).
ULA addresses are not routed to the Internet, and setting up NAT is not as straightforward as with IPv4. This means one cannot route the entire traffic over the tunnel. Those wanting to connect two sites via IPv6, without the need to connect to the Internet over the tunnel, may want to use the ULA addresses for ease.
Alternatively, a NDP proxy should work. See
this StackExchange post
.
After having received a prefix (a /64 is recommended), append the following to the server.conf:
server-ipv6 2001:db8:0:123::/64
This is the IPv6 equivalent to the default 10.8.0.0/24 network of OpenVPN and needs to be taken from the DHCPv6 client. Or use for example fd00:1234::/64.
Those wanting to push a route to a home network (192.168.1.0/24 equivalent), need to also append:
push "route-ipv6 2001:db8:0:abc::/64"
OpenVPN does not yet include DHCPv6, so there is no method to e.g. push DNS server over IPv6. This needs to be done with IPv4. The
OpenVPN Wiki
provides some other configuration options.
Starting OpenVPN
Manual startup
To troubleshoot a VPN connection, start the client's daemon manually with
openvpn /etc/openvpn/client/client.conf
as root. The server can be started the same way using its own configuration file (e.g.,
openvpn /etc/openvpn/server/server.conf
).
systemd service configuration
To start the OpenVPN server automatically at system boot,
enable
openvpn-server@
configuration
.service
on the applicable machine. For a client,
enable
openvpn-client@
configuration
.service
instead. (Leave
.conf
out of the
configuration
string.)
For example, if the client configuration file is
/etc/openvpn/client/
client
.conf
, the service name is
openvpn-client@
client
.service
. Or, if the server configuration file is
/etc/openvpn/server/
server
.conf
, the service name is
openvpn-server@
server
.service
.
Tip
If
openvpn-client@
configuration
.service
units take a long time to start, it might be the network manager is not triggering the
network-online.target
systemd target at the right moment. For example, when using
systemd-networkd
, check that
systemd-networkd-wait-online.service
is properly configured.
Letting NetworkManager start a connection
One 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/sh
case "$2" in
  up)
    if [ "$CONNECTION_ID" = "Provider" ]; then
      systemctl start openvpn-client@
<configuration>
fi
  ;;
  down)
    systemctl stop openvpn-client@
<configuration>
;;
esac
See
NetworkManager#Network services with NetworkManager dispatcher
for more details.
NetworkManager-native VPN configuration
NetworkManager
supports OpenVPN management using
networkmanager-openvpn
.
Note
NetworkManager only support
mobile
configuration files (usually ending in
.ovpn
), i.e with inline certificate and only one file (Linux configurations usually come with a userpass file and a detached certificate).
No error messages are produced for unsupported options, open the
journal
for
networkmanager
to see the used options.
GUI configuration
In your desktop environment
network settings
(or
nm-connection-editor
). Click the plus sign to add a new connection and choose OpenVPN and manually enter the settings. You also can optionally import
#The client configuration profile
by selecting
Import a saved VPN configuration...
and selecting the appropriate file.
CLI configuration
For importing a configuration:
$ nmcli connection import type openvpn file
file
.ovpn
To do a manual configuration:
$ nmcli connection add type vpn vpn-type openvpn ...
See
nm-settings-nmcli(5) § vpn setting
for the detailed options.
If you want to setup login and password, check that there is no
auth-user-pass
line in the openvpn file or remove it. Then after the import:
$ nmcli connection modify
name
\
   +vpn.data "connection-type=password-tls, username=
USERNAME
" \
   vpn.user-name
USERNAME
\
   +vpn.secrets "password=
PASS
"
You will then be able to connect without re-entering the password with:
$ nmcli connection up
name
Sync state with connection
NetworkManager supports syncing the VPN state with a
interface connection state
, i.e start the VPN together with the connection and bringing it down when the connection goes down.
To achieve this, open
nm-connection-editor
and select a network connection (not the VPN), then head to the
General
section, tick
Automatically connect to VPN
and select the appropriate configuration in the dropdown menu.
Automatically connect to VPN via CLI
First, list your connections as follows:
nmcli connection
NAME     UUID                                  TYPE      DEVICE
zrh-003  d46e4a92-778e-4792-b085-e1f638ecb8e3  vpn       enp1s0
enp1s0   1715b889-3c47-3e21-a86f-94ce207297a9  ethernet  enp1s0
tun0     7405f329-255d-4b50-b98d-c2e865a443a4  tun       tun0
Copy the UUID of the VPN Connection you want to connect automatically to (here, d46e4a92-778e-4792-b085-e1f638ecb8e3), then edit the primary connection (here the Ethernet one) to make it use the VPN:
$ nmcli c edit enp1s0
nmcli> set connection.secondaries d46e4a92-778e-4792-b085-e1f638ecb8e3
nmcli> save persistent
Connection 'enp1s0' (1715b889-3c47-3e21-a86f-94ce207297a9) successfully updated.
Afterwards,
restart
NetworkManager.service
Import VPN configuration
With the
openvpn3
AUR
client:
$ openvpn3 config-import --config
path/to/config.conf
To list the configurations:
$ openvpn3 configs-list
Troubleshooting
No certificate password
If you get:
Warning: password for 'vpn.secrets.password' not given in 'passwd-file' and nmcli cannot ask without '--ask' option.
Error: Connection activation failed: No valid secrets
Even with
[vpn]
cert-pass-flags=0
You can add:
[vpn-secrets]
cert-pass=
anything_you_want
Routing client traffic through the server
Without further configuration only traffic directly to and from the OpenVPN server's IP passes through the VPN. To have other traffic, like web traffic pass through the VPN, correspondent routes must be added.  Either add routes in the client's configuration or configure the server to push these routes to the client.
To redirect traffic to and from a subnet of the server, add
push "route <address pool> <subnet>"
right before the
remote <address> <port> udp/tcp
, like:
route 192.168.1.0 255.255.255.0
To redirect all traffic including Internet traffic to the server, add the following in the client's configuration:
redirect-gateway def1 bypass-dhcp ipv6
If running an IPv4-only server, drop the
ipv6
option. If running IPv6-only, use
redirect-gateway ipv6 !ipv4
.
To make the server push routes,
append
push "redirect-gateway def1 bypass-dhcp ipv6"
to the configuration file (i.e.
/etc/openvpn/server/server.conf
)
[4]
of the server. Note this is not a requirement and may even give performance issue:
push "redirect-gateway def1 bypass-dhcp ipv6"
If running an IPv4-only server, drop the
ipv6
option. If running IPv6-only, use
push "redirect-gateway ipv6 !ipv4"
Use the
push "route <address pool> <subnet>"
option to allow clients reaching other subnets/devices behind the server:
push "route 192.168.1.0 255.255.255.0"
push "route 192.168.2.0 255.255.255.0"
Optionally, push local
DNS
settings to clients (e.g. the DNS-server of the router and domain prefix
.internal
):
Note
One may need to use a simple
DNS
forwarder like
BIND
and push the IP address of the OpenVPN server as DNS to clients.
push "dhcp-option DNS 192.168.1.1"
push "dhcp-option DOMAIN internal"
After setting up the configuration file,
enable packet forwarding
on the server. Additionally, the server's
firewall
needs to be adjusted to allow VPN traffic, which is described below for both
ufw
and
iptables
.
Note
There are potential pitfalls when routing all traffic through a VPN server. Refer to the
OpenVPN documentation
for more information.
Firewall configuration
firewalld
If using the default port 1194, enable the
openvpn
service. Otherwise, create a new service with a different port.
# firewall-cmd --zone=public --add-service openvpn
Now add masquerade to the zone:
# firewall-cmd --zone=FedoraServer --add-masquerade
Make these changes permanent:
# firewall-cmd --runtime-to-permanent
ufw
In order to allow
ufw
forwarding (VPN) traffic
append
the following to
/etc/default/ufw
:
/etc/default/ufw
DEFAULT_FORWARD_POLICY="ACCEPT"
Change
/etc/ufw/before.rules
, and
append
the following code after the header and before the "*filter" line:
Change the IP/subnet mask to match the
server
set in the OpenVPN server configuration.
Change the
network interface
to the connection used by OpenVPN server.
/etc/ufw/before.rules
# NAT (Network Address Translation) table rules
*nat
:POSTROUTING ACCEPT [0:0]

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

# Optionally duplicate this line for each subnet if your setup requires it
-A POSTROUTING -s 10.8.1.0/24 -o
interface
-j MASQUERADE

# do not delete the "COMMIT" line or the NAT table rules above will not be processed
COMMIT

# Don't delete these required lines, otherwise there will be errors
*filter
Make sure to open the chosen OpenVPN port (default 1194/udp):
# ufw allow 1194/udp
To apply the changes.
reload
/
restart
ufw:
# ufw reload
iptables
In order to allow VPN traffic through an
iptables
firewall, first create an iptables rule for NAT forwarding
[5]
on the server. An example (assuming the interface to forward to is named
eth0
):
# iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
If running multiple servers on different IP pools, add a corresponding line for each one, for example:
# iptables -t nat -A POSTROUTING -s 10.8.1.0/24 -o eth0 -j MASQUERADE
If the server cannot be pinged through the VPN, one may need to add explicit rules to open up TUN/TAP interfaces to all traffic. If that is the case, do the following
[6]
:
Warning
There are security implications for the following rules if one does not trust all clients which connect to the server. Refer to the
OpenVPN documentation on this topic
for more details.
# iptables -A INPUT -i tun+ -j ACCEPT
# iptables -A FORWARD -i tun+ -j ACCEPT
# iptables -A INPUT -i tap+ -j ACCEPT
# iptables -A FORWARD -i tap+ -j ACCEPT
Additionally be sure to accept connections from the OpenVPN port (default 1194) and through the physical interface:
# iptables -A INPUT -i eth0 -m state --state NEW -p udp --dport 1194 -j ACCEPT
# iptables -A FORWARD -i tun+ -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A FORWARD -i eth0 -o tun+ -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A FORWARD -i tap+ -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A FORWARD -i eth0 -o tap+ -m state --state RELATED,ESTABLISHED -j ACCEPT
When satisfied, make the changes permanent as shown in
iptables#Configuration and usage
.
Those with multiple
tun
or
tap
interfaces, or more than one VPN configuration can "pin" the name of the interface by specifying it in the OpenVPN configuration file, e.g.
tun22
instead of
tun
. This is advantageous if different firewall rules for different interfaces or OpenVPN configurations are wanted.
Prevent leaks if VPN goes down
This prevents all traffic through the default interface (enp3s0 for example) and only allows traffic through tun0.
If the OpenVPN connection drops, the system will lose its internet access thereby preventing connections through the default network interface.
One may want to set up a script to restart OpenVPN if it goes down.
ufw
# Default policies
 ufw default deny incoming
 ufw default deny outgoing

 # Openvpn interface (adjust interface accordingly to your configuration)
 ufw allow in on tun0
 ufw allow out on tun0

 # Local Network (adjust ip accordingly to your configuration)
 ufw allow in on enp3s0 from 192.168.1.0/24
 ufw allow out on enp3s0 to 192.168.1.0/24

 # Openvpn (adjust port accordingly to your configuration)
 ufw allow in on enp3s0 from any port 1194
 ufw allow out on enp3s0 to any port 1194
Warning
DNS
will not
work
unless
running a dedicated DNS server like
BIND
.
Alternatively, one can allow DNS leaks.
Be sure to trust your DNS server!
# DNS
 ufw allow in from any to any port 53
 ufw allow out from any to any port 53
vpnfailsafe
Alternatively, the
vpnfailsafe
(
vpnfailsafe-git
AUR
) script can be used by the client to prevent DNS leaks and ensure that all traffic to the internet goes over the VPN. If the VPN tunnel goes down, internet access will be cut off, except for connections to the VPN server(s). The script contains the functionality of
update-resolv-conf
, so the two do not need to be combined.
dhcpcd
redirect-gateway
adds special routes to the system routing table. If running
dhcpcd
and the local DHCP configuration changes, perhaps because the Wi-Fi access point has changed, then
dhcpcd
will delete all of these special routes. The easiest way to restore them is to prompt
openvpn
to reconnect, using
/etc/dhcpcd.exit-hook
:
# Prompt openvpn to reconnect when the network reconnects.
if $if_configured && $if_up && [ "$reason" != ROUTERADVERT ]; then
    state="$(systemctl show -P ActiveState openvpn-client@config)"
    if [ "$state" == 'active' ]; then
        pid="$(systemctl show -P MainPID openvpn-client@config)"
        kill -USR1 "$pid"
    fi
fi
Replace
@config
with the name of your client config.
Layer-3 IPv4 routing
This section describes how to connect client/server LANs to each other using Layer-3 IPv4 routing.
Prerequisites for routing a LAN
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. See
Internet sharing#Enable packet forwarding
for configuration details.
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 in
Talk:OpenVPN
)
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/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 configuration file.
The CCD folder must be accessible via user and group defined in the server configuration file (typically nobody:nobody)
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/server.conf
client-config-dir ccd
route 192.168.4.0 255.255.255.0
If accessing a machine in the client LAN from a machine in the server LAN, remember that packet forwarding needs to be enabled on the client (
Internet sharing#Enable packet forwarding
).
Note
If running openVPN as a daemon with systemd, you may need to specify an absolute path to your
ccd
directory.
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/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/server.conf
client-to-client
In order for another client or client LAN to see a specific client LAN, 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/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
One may need to adjust the
firewall
to allow client traffic passing through the VPN server.
DNS
For Linux, the OpenVPN client can receive DNS host information from the server, but the client expects an external command to act on this information. No such commands are configured by default. They must be specified with the
up
and
down
options. There are a few alternatives for what scripts to use, but none are officially recognised by OpenVPN, so in order for any of them to work,
script-security
must be set to 2. The
down-root
plugin can be used instead of the
down
option if
running as an unprivileged user
.
The pull-resolv-conf custom scripts
These scripts are
maintained by
[
dead link
2025-11-17—HTTP 404]
OpenVPN. They are
client.up
and
client.down
, and they are packaged in
/usr/share/openvpn/contrib/pull-resolv-conf/
. The following is an excerpt of a resulting client configuration using the scripts in conjunction with the
down-root
plugin:
/etc/openvpn/client/
clienttunnel
.conf
user nobody
group nobody
# Optional, choose a suitable path to chroot into
chroot /srv
script-security 2
up /usr/share/openvpn/contrib/pull-resolv-conf/client.up 
plugin /usr/lib/openvpn/plugins/openvpn-plugin-down-root.so "/usr/share/openvpn/contrib/pull-resolv-conf/client.down tun0"
These scripts use the
resolvconf
command if present.
systemd-resolvconf
and
Openresolv
both implement this command. See their wiki pages for more information on getting a working
resolvconf
implementation.
Note
As of October 2019, systemd-resolvconf works as long as the systemd-resolved service is running. Openresolv will not work out of the box because
client.up
will only create private DNS server entries. These require extra configuration of openresolv to work. See
resolvconf(8)
for more details on private DNS servers in openresolv.
If no implementation of
resolvconf
is present,
client.up
preserves the existing
resolv.conf
at
/etc/resolv.conf.ovpnsave
and writes a new one. This new one will not have any of the original DNS servers.
When editing these scripts, copy them somewhere else and edit them there, so that the changes do not get overwritten by the next
openvpn
package upgrade.
/etc/openvpn/client/
is a pretty good place.
# cp /usr/share/openvpn/contrib/pull-resolv-conf/* /etc/openvpn/client/
Edit
/etc/openvpn/client/client.up
and
/etc/openvpn/client/client.down
.
The update-resolv-conf custom script
Note
Another script,
update-systemd-resolved
, is recommended by the author of update-resolv-conf for systems with systemd.
The
openvpn-update-resolv-conf
script is available as an alternative to packaged scripts. It needs to be saved for example at
/etc/openvpn/update-resolv-conf
and made
executable
.
Users preferring a package may use
openvpn-update-resolv-conf-git
AUR
but will still need to do the following:
Once the script is installed add lines like the following into the OpenVPN client configuration file:
script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf
Note
If manually placing the script on the filesystem, be sure to have
openresolv
installed.
Now, when launching the OpenVPN connection,
resolv.conf
should be updated accordingly, and also should get returned to normal when the connection is closed.
Note
When using
openresolv
with the
-p
or
-x
options in a script (as both the included
client.up
and
update-resolv-conf
scripts currently do), a DNS resolver like
dnsmasq
or
unbound
is required for
openresolv
to correctly update
/etc/resolv.conf
.  In contrast, when using the default DNS resolution from
libc
the
-p
and
-x
options must be removed in order for
/etc/resolv.conf
to be correctly updated by
openresolv
.
For example, if the script contains a command like
resolvconf -p -a
and the default DNS resolver from
libc
is being used, change the command in the script to be
resolvconf -a
.
The update-systemd-resolved custom script
Note
Since
systemd
229,
systemd-networkd
has exposed an API through DBus allowing management of DNS configuration on a per-link basis. Tools such as
openresolv
may not work reliably when
/etc/resolv.conf
is managed by
systemd-resolved
, and will not work at all if using
resolve
instead of
dns
in
/etc/nsswitch.conf
.
The
update-systemd-resolved
script links OpenVPN with
systemd-resolved
via DBus to update the DNS records.
Copy the script into
/etc/openvpn/scripts
and mark as
executable
(or
install
openvpn-update-systemd-resolved
AUR
) and
append
the following lines into the OpenVPN client configuration file:
/etc/openvpn/client/client.conf
client
remote example.com 1194 udp

script-security 2
setenv PATH /usr/bin
up /etc/openvpn/scripts/update-systemd-resolved
down /etc/openvpn/scripts/update-systemd-resolved
down-pre
In order to send all DNS traffic through the VPN tunnel and prevent DNS leaks, also add the following line (see
[7]
):
/etc/openvpn/client/client.conf
dhcp-option DOMAIN-ROUTE .
Make sure that the
systemd-resolved
service is configured and running. Also, since openvpn 2.5.0-3 scripts are running as openvpn user instead of root. Thus, add a PolicyKit rule to allow OpenVPN systemd units to call DBus with SetLinkDNS:
/etc/polkit-1/rules.d/00-openvpn-resolved.rules
polkit.addRule(function(action, subject) {
    if (action.id == 'org.freedesktop.resolve1.set-dns-servers' ||
        action.id == 'org.freedesktop.resolve1.set-domains' ||
        action.id == 'org.freedesktop.resolve1.set-dnssec') {
        if (subject.user == 'openvpn') {
            return polkit.Result.YES;
        }
    }
});
Note
When using the
openvpn-update-systemd-resolved
AUR
package, the path to the
update-systemd-resolved
script in
client.conf
should be changed from
/etc/openvpn/scripts/
to
/usr/bin/
and polkit rules are already set up.
Override DNS servers using NetworkManager
By default
networkmanager-openvpn
plugin appends DNS servers provided by OpenVPN to
/etc/resolv.conf
.
To verify that the correct DNS server(s) are configured, see
resolvectl status
if systemd-resolved is in use, for other resolvers see
Domain name resolution
.
Layer-2 Ethernet bridging
Establishing an Ethernet bridge enables access to other devices within a subnet of the server. For example, accessing other machines in the local network of the OpenVPN server via
Samba
would be possible with this approach. Clients would be assigned an IP address as if it were within the same subnet.
This is generally a two step process: 1) establishing the tap interface and the network bridge on the OpenVPN server to bridge the tap interface and the Ethernet interface, and 2) configuring the OpenVPN server.
See
OpenVPN Bridge
.
Configuration generators
Warning
Users are highly recommended to pass through the manual configuration described above to gain knowledge about options and usage before using any additional automation scripts.
ovpngen
The
ovpngen
AUR
package provides a simple shell script that creates OpenVPN compatible tunnel profiles in the unified file format suitable for the OpenVPN Connect app for Android and iOS.
Simply invoke the script with 5 tokens:
Server Fully Qualified Domain Name of the OpenVPN server (or IP address).
Full path to the CA cert.
Full path to the client cert.
Full path to the client private key.
Full path to the server TLS shared secret key.
Optionally a port number.
Optionally a protocol (udp or tcp).
Example:
# ovpngen example.org /etc/openvpn/server/ca.crt /etc/easy-rsa/pki/signed/client1.crt /etc/easy-rsa/pki/private/client1.key /etc/openvpn/server/ta.key > foo.ovpn
If the server is configured to use tls-crypt, as is suggested in
#The server configuration file
,
manually edit
the resulting
foo.ovpn
replacing
<tls-auth>
and
</tls-auth>
with
<tls-crypt>
and
</tls-crypt>
.
The resulting
foo.ovpn
can be edited if desired as the script does insert some commented lines.
foo.ovpn
will not automatically route all traffic through the VPN, so consider following
#Routing client traffic through the server
to enable redirection.
The client expects this file to be located in
/etc/openvpn/client/foo.conf
. Note the change in file extension from 'ovpn' to 'conf' in this case.
Tip
If the server.conf contains a specified cipher and/or auth line, it is highly recommended that users manually edit the generated .ovpn file adding matching lines for cipher and auth.  Failure to do so may results in connection errors!
openvpn-unroot
Note
If using a custom script, perhaps for configuring
#DNS
, add these scripts to the configuration before calling openvpn-unroot on it. Failing to do so will cause problems if the scripts require root permissions.
The steps necessary for OpenVPN to
#Run as unprivileged user
, can be performed automatically using
openvpn-unroot
(
openvpn-unroot-git
AUR
).
It automates the actions required for the
OpenVPN howto
by adapting it to systemd, and also working around the bug for persistent tun devices mentioned in the note.
Troubleshooting
Client daemon not reconnecting after suspend
openvpn-reconnect
AUR
, available on the AUR, solves this problem by sending a SIGHUP to openvpn after waking up from suspend.
Alternatively, restart OpenVPN after suspend by creating the following systemd service:
/etc/systemd/system/openvpn-reconnect.service
[Unit]
Description=Restart OpenVPN after suspend

[Service]
ExecStart=/usr/bin/pkill --signal SIGHUP --exact openvpn

[Install]
WantedBy=sleep.target
Enable
this service for it to take effect.
Connection drops out after some time of inactivity
If the VPN-Connection drops some seconds after it stopped transmitting data and, even though it states it is connected, no data can be transmitted through the tunnel, try adding a
keepalive
directive to the server's configuration:
/etc/openvpn/server/server.conf
keepalive 10 120
In this case the server will send ping-like messages to all of its clients every 10 seconds, thus keeping the tunnel up.
If the server does not receive a response within 120 seconds from a specific client, it will assume this client is down.
A small ping-interval can increase the stability of the tunnel, but will also cause slightly higher traffic. Depending on the connection, also try lower intervals than 10 seconds.
PID files not present
The default systemd service file for openvpn-client does not have the --writepid flag enabled, despite creating /run/openvpn-client. If this breaks a configuration (such as an i3bar VPN indicator), simply change
openvpn-client@.service
using a
drop-in snippet
:
[Service]
ExecStart=
ExecStart=/usr/sbin/openvpn --suppress-timestamps --nobind --config %i.conf --writepid /run/openvpn-client/%i.pid
Route configuration fails with systemd-networkd
When using
systemd-networkd
to manage network connections and attempting to tunnel all outgoing traffic through the VPN, OpenVPN may fail to add routes. This is a result of systemd-networkd attempting to manage the tun interface before OpenVPN finishes configuring the routes. When this happens, the following message will appear in the OpenVPN log.
openvpn[458]: RTNETLINK answers: Network is unreachable
openvpn[458]: ERROR: Linux route add command failed: external program exited with error status: 2
From systemd-233, systemd-networkd can be configured to ignore the tun connections and allow OpenVPN to manage them. To do this, create the following file:
/etc/systemd/network/90-tun-ignore.network
[Match]
Name=tun*

[Link]
Unmanaged=true
Restart
systemd-networkd.service
to apply the changes. To verify that the changes took effect, start the previously problematic OpenVPN connection and run
networkctl
. The output should have a line similar to the following:
7 tun0             none               routable    unmanaged
tls-crypt unwrap error: packet too short
This error shows up in the server log when a client that does not support tls-crypt, or a client that is misconfigured to use tls-auth while the server is configured to use tls-crypt, attempts to connect.
To support clients that do not support tls-crypt, replace
tls-crypt ta.key
with
tls-auth ta.key 0
(the default) in
server.conf
. Also replace
tls-crypt ta.key
with
tls-auth ta.key 1
(the default) in
client.conf
.
NetworkManager fails to connect using imported configuration
There is a known upstream bug
[8]
[9]
[10]
in conjunction with importing existing OpenVPN configurations (
.ovpn
files) under KDE via the GUI (
plasma-nm
not
nm-connection-editor
) that causes certain advanced options such as
tls-crypt
to be silently ignored. The created NetworkManager connection profile will therefore be incomplete and the connection ultimately fails.
Logs might reveal errors such as the following:
TLS Error: TLS handshake failed
TLS Error: TLS key negotiation failed to occur within 60 seconds (check your network connectivity)
A workaround is to resort to NetworkManager's command-line utility
nmcli
to import the connection profile as is shown in
#CLI configuration
.
OpenVPN connection fails after update to OpenSSL3
There exists an issue with PKCS#12 encoded user certificates/private key files (usually denoted by a
.pfx
or
.p12
file ending) with OpenSSL3, c.f. also
[11]
. This leads to connections which worked perfectly before updating to OpenSSL3 not being able to connect with the following log messages produced (in this case via NetworkManager):
nm-openvpn[14025]: WARNING: No server certificate verification method has been enabled.  See
https://openvpn.net/howto.html#mitm
for more info.
nm-openvpn[14025]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
nm-openvpn[14025]: OpenSSL: error:0308010C:digital envelope routines::unsupported
nm-openvpn[14025]: OpenSSL: error:11800071:PKCS12 routines::mac verify failure
nm-openvpn[14025]: Decoding PKCS12 failed. Probably wrong password or unsupported/legacy encryption
nm-openvpn[14025]: SIGUSR1[soft,private-key-password-failure] received, process restarting
The reason is that older versions of OpenSSL used algorithms, which are now deprecated, to encrypt the PKCS#12 files.
To solve this issue the PKCS#12 file must be re-encrypted with a non-legacy algorithm.
$ cd path/to/the/pfx-file
$ mv mykeys.pfx mykeys.pfx.bak
$ openssl pkcs12 -in mykeys.pfx.bak -out mykeys.pfx -aes256 -legacy
See also
Wikipedia:OpenVPN