Complete OpenVPN 2.0 and 2.2 Server Installation and Configuration Tutorial

Today i'm going to write about OpenVPN server and its implementation. OpenVPN is a stable VPN solution that use SSL/TLS encryption technologies with cost effective and ideal for IT companies.

This tutorial show you the step by step Installation and configuration of a perfect Open VPN Server in Linux. This OpenVPN server configuration tutorial Includes implementation of  OpenVPN server without bridging technology.

The Requirement

  Build an Open VPN server in a linux distribution(CentOS), and allows clients systems from web(www) can connect to the Open VPN server and create an encrypted vpn tunnel with server and become a part of the local LAN of VPN server. So the other systems in the LAN and vpn client can communicate each other with no limits.

You must have a latest fedora/CentOS machine, 2 NIC cards, Static Public ip address.

Implementing environment

OpenVPN server public ip address: 170.213.235.26

OpenVPN server's LAN ip address: 192.168.10.50   
(VPN server's LAN ip address range : 192.168.10.0/255.255.255.0) 

Open VPN server's TAP interface ip address: 10.50.30.1 

IP address range reserved for VPN clients :  10.50.30.0/255.255.255.0

(Please note: this tutorial is based on redhat/fedora/centos)

Step1: Installing OpenVPN server
Install 2 required packages "openvpn" and "bridge-utils" (or install from epel repo)

[root@server ~]# yum install openvpn
[root@server ~]# yum install bridge-utils


Or install from EPEL repository, Read my article about Install EPEL first

[root@server ~]# yum --enablerepo=epel install openvpn
[root@server ~]# yum --enablerepo=epel install bridge-utils


Copy the main configuration file "server.conf"  to directory /etc/openvpn/
(Replace x.x.x with exat OpenVPN directory name)
[root@server ~]# cp /usr/share/doc/openvpn-x.x.x/sample-config-files/server.conf /etc/openvpn/

Edit the server.conf file

[root@server ~]# vi /etc/openvpn/server.conf

#In 53rd line edit like below (tap "zero")

dev tap0

#In  78th, 79th, 80th lines, edit like below

ca /etc/openvpn/easy-rsa/keys/ca.crt

cert /etc/openvpn/easy-rsa/keys/server.crt

key /etc/openvpn/easy-rsa/keys/server.key 

#In 87th line 

dh /etc/openvpn/easy-rsa/keys/dh1024.pem

#In the 96th line (specify reserving OpenVPN client address range)
#This address range is assaigned to clients by server.

server 10.50.30.0 255.255.255.0     

#In the 103rd line Disable it by adding a "#"

#ifconfig-pool-persist ipp.txt

#In the 275th line edit like below

status status.log 5

#In the 276th line add the below

status-version 2

#In the 285th line enable the line by removing the ";"  and edit like below

log-append /var/log/openvpn.log

#Now save the server.conf file

Step2: Create Certificate Authority(CA) Certificates and Keys


Copy all the files in /usr/share/openvpn/easy-rsa/2.0  to /etc/openvpn/easy-rsa/
[root@server ~]# cp -R /usr/share/openvpn/easy-rsa/2.0 /etc/openvpn/easy-rsa


Change default directory to /etc/openvpn/easy-rsa/
[root@server ~]# cd /etc/openvpn/easy-rsa/


Create a Directory named "keys"
[root@server easy-rsa]# mkdir keys


#Edit the vars file and Add VPN Server's Organisation informations in line 64th to 68th.
[root@server easy-rsa ]# vi vars

export KEY_COUNTRY="USA"
export KEY_PROVINCE="Newyork"                                    
export KEY_CITY="NewYork"
export KEY_ORG="Servercomputing"
export KEY_EMAIL="na@na.com"# Now save the vars file

Run the below commands

[root@server easy-rsa]# source ./vars

**************************************************************
  No /etc/openvpn/easy-rsa/openssl.cnf file could be found
  Further invocations will fail
**************************************************************
NOTE: If you run ./clean-all, I will be doing a rm -rf on /etc/openvpn/easy-rsa/keys

Here the above command failed to ececute due to openssl.cnf is not found in the /etc/openvpn/easy-rsa directory.  You need to rename the file /etc/openvpn/easy-rsa/openssl-1.0.0.cnf to openssl.cnf.
[root@server easy-rsa]#cp /etc/openvpn/easy-rsa/openssl-1.0.0.cnf /etc/openvpn/easy-rsa/openssl.cnf

Now execute the "source ./vars" command again (see below)
[root@server easy-rsa]# source ./vars
NOTE: If you run ./clean-all, I will be doing a rm -rf on /etc/openvpn/easy-rsa/keys

[root@server easy-rsa]# ./clean-all

[root@server easy-rsa]# ./build-ca

Generating a 1024 bit RSA private key
.....................++++++
...++++++
writing new private key to 'ca.key'
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
#Press enterCountry Name (2 letter code) [US]:                    
State or Province Name (full name) [Newyork]:  #Press enter      
Locality Name (eg, city) [NewYork]:                  #Press enter
Organization Name (eg, company) [Servercomputing]:    #Press enter
Organizational Unit Name (eg, section) [changeme]:       #Press enter
Common Name (eg, your name or your server's hostname) [changeme]:servercomputing                                         #Type "FQDN"
Name [changeme]:server-ca                         #Type server-ca
Email Address [mail@host.domain]:              #Press enter

Now ca.crt and ca.key is created in /etc/openvpn/easy-rsa/keys/ directory.
ca.crt is required in VPN client computer to make vpn connection to server. So transfer it to VPN client machine.

Step3:  Create Server certificates and keys

[root@server easy-rsa]# ./build-key-server server
Generating a 1024 bit RSA private key
........................++++++
....................................++++++

writing new private key to 'server.key'

-----

You are about to be asked to enter information that will be incorporated

into your certificate request.

What you are about to enter is what is called a Distinguished Name or a DN.

There are quite a few fields but you can leave some blank

For some fields there will be a default value,

If you enter '.', the field will be left blank.

-----

Country Name (2 letter code) [US]:                            #Press enter

State or Province Name (full name) [Newyork]:          #Press enter

Locality Name (eg, city) [NewYork]:                          #Press enter

Organization Name (eg, company) [Servercomputing]:   #Press enter

Organizational Unit Name (eg, section) [changeme]:      #Press enter

Common Name (eg, your name or your server's hostname) [server]:servercomputing      #input FQDN

Name [changeme]:server                 #Type "server"

Email Address [mail@host.domain]:   #Press enter

Please enter the following 'extra' attributes

to be sent with your certificate request

A challenge password []:12345                 #input any password 

An optional company name []:          #Press enter

Using configuration from /etc/openvpn/easy-rsa/openssl.cnf

Check that the request matches the signature

Signature ok

The Subject's Distinguished Name is as follows

countryName           :PRINTABLE:'US'

stateOrProvinceName   :PRINTABLE:'Province'

localityName          :PRINTABLE:'NewYork'

organizationName      :PRINTABLE:'Servercomputing'

organizationalUnitName:PRINTABLE:'changeme'

commonName            :PRINTABLE:'servercomputig'

name                  :PRINTABLE:'server'

emailAddress          :IA5STRING:'mail@host.domain'

Certificate is to be certified until Apr  1 07:37:52 2022 GMT (3650 days)

Sign the certificate? [y/n]:y        #Press Y

1 out of 1 certificate requests certified, commit? [y/n]y      #Press Y

Write out database with 1 new entries

Data Base Updated

Step4    Generate a Diffie Hellman (DH) parameter

Generate Diffie Hellman ( DH ) parameter

[root@server easy-rsa]# ./build-dh

Generating DH parameters, 1024 bit long safe prime, generator 2

This is going to take a long time

..........................+.....................................................+.................................................+......................+.....................................+..........................................+..........

(Will take about 20-30secs...)

Step5 Generate Keys and Certificates for VPN clients

Edit the vars file and add the VPN client's Country, Organisation, Email and other information. in line 64 to 68th.

[root@server easy-rsa]# vim vars

export KEY_COUNTRY="UK"

export KEY_PROVINCE="Province"

export KEY_CITY="London"

export KEY_ORG="Servercomputing1"

export KEY_EMAIL="na@na.com"

# Now save the vars file

[root@server easy-rsa]# source ./vars
NOTE: If you run ./clean-all, I will be doing a rm -rf on /etc/openvpn/easy-rsa/keys

[root@server easy-rsa]# ./build-key-pass ukclient
Generating a 1024 bit RSA private key
..............++++++
...++++++
writing new private key to 'ukclient.key'
Enter PEM pass phrase:                                 #Enter a password to authenticate for VPN client
Verifying - Enter PEM pass phrase:                       #Re enter the password
-----
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----

Country Name (2 letter code) [UK]:                           #Press Enter

State or Province Name (full name) [Province]:         #Press Enter

Locality Name (eg, city) [London]:                            #Press Enter

Organization Name (eg, company) [Servercomputing1]:      #Press Enter

Organizational Unit Name (eg, section) [changeme]:           #Press Enter

Common Name (eg, your name or your server's hostname) [ukclient]:London-UK     # a name to easily identify the VPN client

Name [changeme]:ukclient                          # Same as in the command

Email Address [mail@host.domain]:        #Press Enter

Please enter the following 'extra' attributes

to be sent with your certificate request

A challenge password []:12345                      #type a password

An optional company name []:                      #Press Enter

Using configuration from /etc/openvpn/easy-rsa/openssl.cnf

Check that the request matches the signature

Signature ok

The Subject's Distinguished Name is as follows

countryName           :PRINTABLE:'UK'

stateOrProvinceName   :PRINTABLE:'Province'

localityName          :PRINTABLE:'London'

organizationName      :PRINTABLE:'Servercomputing1'

organizationalUnitName:PRINTABLE:'changeme'

commonName            :PRINTABLE:'London-UK'

name                  :PRINTABLE:'ukclient'

emailAddress          :IA5STRING:'mail@host.domain'

Certificate is to be certified until Apr  1 10:04:09 2022 GMT (3650 days)

Sign the certificate? [y/n]:y               #Press y

1 out of 1 certificate requests certified, commit? [y/n]y               #Press y

Write out database with 1 new entries

Data Base Updated

#ukclient.crt and ukclient.key is now created in /etc/openvpn/easy-rsa/keys/ directory

transfer the two files to VPN clients           

Step6:  Start OpenVPN Server

[root@server easy-rsa]# service openvpn start

Starting openvpn: [ OK ]

Add OpenVPN to system Startup
[root@server easy-rsa]# chkconfig openvpn on

Step7: Client side Configuration
Download and install the OpenVPN client installer file from the below Link
OpenVPN client Download link (works with WindowsXP,Vista and Windows7)
Note: Installing client and initializing the VPN connection requires Administrator privileges.
After installatling OpenVPN client, Copy C:\Program Files\OpenVPN\sample-config\client.ovpn  to  C:\Program Files\OpenVPN\config\client.ovpn 
And open the client.ovpn file and edit like below

Click on screenshot to enlarge

client
proto tcp
dev tap0
remote 170.213.235.26 1194
resolv-retry infinite
nobind
persist-key
persist-tun
ca ca.crt
cert ukclient.crt
key ukclient.key
comp-lzo
verb 3

#And save the client.ovpn file

#Note above 170.213.235.26 is OpenVPN server's WAN interface ip address and 1194 is the TCP port number which Server listens.

Now copy the ca.crt (created in step2), ukclient.crt, ukclient.key (created in step 5) to C:\Program Files\OpenVPN\config\  folder



Now double click on the OpenVPN GUI short cut on desktop and click on "connect" by right click on the openvpn client tray icon

And input the password when prompted (password is configured in step5 as "PEM Pass phrase")

Step8:  Test client-Server connectivity

Test Connectivity by ping to server from client

Step9:  Establish ip forwarding in Server

                Now the connectivity is only between the VPN server anc VPN client. Other systems in the Servers's LAN cannot connect the VPN client and vice versa.
But the ultimate goal is VPN client can access all other PCs in the Server's LAN range and also All the systems in LAN can access the VPN client also. To do this the OpenVPN server can act as a router to forward ip packets from LAN to VPN client.

Run the following 4 commands   

[root@server easy-rsa]# echo 1 > /proc/sys/net/ipv4/ip_forward

[root@server easy-rsa]# iptables -I FORWARD -o tap0 -j ACCEPT

[root@server easy-rsa]# service iptables save

[root@server easy-rsa]# service iptables restart

Now add the OpenVPN server's LAN ipaddress (192.168.10.50) as default gateway in all systems in the LAN.

Now all the systems in the VPNServer's LAN can communicate with the VPN clients.

Test it by ping to 10.50.30.2 from LAN systems....

Thanks for visiting and add your comments...............

LABELS: CentOS, Linux-server, OpenVPN, VPN