Nainstalujeme balíček openvpn na server a na klienty.

Na serveru najdeme adresář pro tvorbu certifikátů (viz manual), překopírujeme ho do adresáře /etc/openvpn, upravíme co je třeba (viz manuál), změníme práva na spustitelné a vytvoříme požadovaný počet certifikátů. Certifikáty rozdistribujeme podle manualu na server a klienty.

Vzorový konfigurační soubor – server.conf:

local přidělena.vnejsi.pevnaIP.adresa_serveru (nebo jeho nazev)
port 1194
proto udp
dev tun
ca ca.crt
cert server.crt
key server.key 
dh dh1024.pem
server 10.8.0.0 255.255.255.0 # napriklad
ifconfig-pool-persist /etc/openvpn/ipp.txt
client-config-dir ccd
client-to-client
keepalive 10 120
comp-lzo
persist-key
persist-tun
status /var/log/openvpn/openvpn_status.log
verb 3

Vzorový konfigurační soubor – client1.conf:

remote přidělena.vnejsi.pevnaIP.adresa_serveru (nebo jeho nazev) 1194
client
dev tun
proto udp
resolv-retry infinite
nobind
persist-key
persist-tun
mute-replay-warnings
ca ca.crt
cert client1.crt
key client1.key
comp-lzo
verb 3
route iprozsah a maska vnitrni site. Napr: 192.168.1.0 255.255.255.0

Obsah /etc/openvpn/ccd (soubor client1):

# ifconfig-push 10.8.0.25 10.8.0.26
# prvni cislo je adresa klienta, druhe adresa serverove casti tunelu.
# jmena souboru musi odpovidat cn polozce v certifikatu. do toho ccd jde toho nacpat vic, napr. iroute atd.

Podrobnosti:

server.conf:

local přidělena.vnejsi.pevnaIP.adresa_serveru (nebo jeho nazev)
port 1194
proto udp
dev tun

ca ca.crt
cert server.crt
key server.key  # This file should be kept secret
dh dh1024.pem

# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.

server 10.8.0.0 255.255.255.0 # napriklad 😉

# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist /etc/openvpn/ipp.txt
#ifconfig-pool-persist ipp.txt

# Configure server mode for ethernet bridging.
# You must first use your OS’s bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100

# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push „route 192.168.10.0 255.255.255.0“
;push „route 192.168.20.0 255.255.255.0“
#push „route 192.168.1.0 255.255.255.0“

# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory „ccd“ for client-specific
# configuration files (see man page for more info).

# EXAMPLE: Suppose the client
# having the certificate common name „Thelonious“
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious‘ private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using „dev tun“ and „server“ directives.

# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2

# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script

# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# the TUN/TAP interface to the internet in
# order for this to work properly).
# CAVEAT: May break client’s network config if
# client’s local DHCP server packets get routed
# through the tunnel.  Solution: make sure
# client’s local DHCP server is reachable via
# a more specific route than the default route
# of 0.0.0.0/0.0.0.0.
#push „redirect-gateway“

# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
;push „dhcp-option DNS 10.8.0.1“
;push „dhcp-option WINS 10.8.0.1“

#client-to-client

keepalive 10 120

comp-lzo

# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100

# It’s a good idea to reduce the OpenVPN
# daemon’s privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody

# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun

# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
# status openvpn-status.log
status /var/log/openvpn/openvpn_status.log

# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the „\Program Files\OpenVPN\log“ directory).
# Use log or log-append to override this default.
# „log“ will truncate the log file on OpenVPN startup,
# while „log-append“ will append to it.  Use one
# or the other (but not both).

# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3

# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20

# ==== z puvodni konfigurace ====
# #local 88.146.181.141
# local 192.168.100.1
# port 1194
# proto udp
# dev tun
# ######secret static.key
# ca ca.crt
# cert server.crt
# key server.key
# dh dh2048.pem
# server 192.168.100.0 255.255.255.0
# ######
# ifconfig-pool-persist ipp2.txt 0
# push „route 192.168.1.0 255.255.255.0“
# #push „redirect-gateway“
# client-to-client
# keepalive 10 120
# tls-auth ta.key 0
# user nobody
# group nogroup
# duplicate-cn
# comp-lzo
# persist-tun
# persist-key
# ping-timer-rem
# verb 3
# nastaveni prav
# user openvpn
# group openvpn
#

Vzorový konfigurační soubor – klient:

remote přidělena.vnejsi.pevnaIP.adresa_serveru (nebo jeho nazev) 1194
client
dev tun
proto udp
# Keep trying indefinitely to resolve the
# host name of the OpenVPN server.  Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
resolv-retry infinite

# Most clients don’t need to bind to
# a specific local port number.
nobind

# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nobody

# Try to preserve some state across restarts.
persist-key
persist-tun

# Wireless networks often produce a lot
# of duplicate packets.  Set this flag
# to silence duplicate packet warnings.
mute-replay-warnings

ca ca.crt
cert client1.crt
key client1.key

comp-lzo

# Set log file verbosity.
verb 3

# Silence repeating messages
;mute 20

# musime routovat do lokalni podsite serveru.
# Tuto routu zadavame zde na klientovi např:..
route 192.168.1.0 255.255.255.0
|

Z poznámek:
ifconfig-pool-persist je hezka vec, ale neudeluje staticke adresy.
Pouze se snazi udelit klientum stejnou adresu, jakou meli minule (např. při přerušení spojení).
Pro opravdu staticke adresy lze použít direktivu client-config-dir.
V .conf souboru na serveru a pak v adresari ccd jsou soubory pro kazdeho klienta v tomto duchu:
cat /etc/openvpn/ccd/client1
ifconfig-push 10.8.0.25 10.8.0.26

Prvni cislo je adresa klienta, druhe adresa serverove casti tunelu.
Jmena souboru musi odpovidat cn polozce v certifikatu.
Pozn: Do toho ccd jde toho nacpat vic, napr. iroute atd.