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Thread: Configuring OpenVPN for internet access

  1. #1
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    Question Configuring OpenVPN for internet access

    Hello!

    After several hours I finally have a working connection between my laptop (client) and my Ubuntu 12.04 server set up with OpenVPN. However, the laptop (running Windows 7 x64) lists the vpn connection as an "Unidentified network" (public) and I cannot use it for internet access (i.e. when I check whatismyipaddress.com, I still get the real one, and not that of the server).

    Could you please help me finish the configuration so that I could use the vpn tunnel for accessing the internet?

    Thanks a lot in advance! Do let me know if you need me to supply any additional details.

  2. #2
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    Re: Configuring OpenVPN for internet access

    Did you add the correct lines in the config on the server side?

    To send all traffic over the VPN tunnel you need to add:

    Code:
    push "redirect-gateway def1"
    Don't forget to enable IP forwarding:
    Code:
    echo "1" > /proc/sys/net/ipv4/ip_forward
    And add a firewall rule to NAT the traffic from your VPN network.
    Code:
    iptables -t nat -A POSTROUTING -s 10.0.8.0/24 -o eth0 -j SNAT --to EXTERNAL_IP

  3. #3
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    Re: Configuring OpenVPN for internet access

    The first two are done, though I enabled IPv4 forwarding in a slightly different manner.
    As for the third, here's what I have in ufw.before rules:

    Code:
    # NAT table rules
    *nat
    :POSTROUTING ACCEPT [0:0]
    # Allow forward traffic from OpenVPN client to eth0
    -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
    Also, here is my server config just in case:

    Code:
    ################################################## Sample OpenVPN 2.0 config file for            #
    # multi-client server.                          #
    #                                               #
    # This file is for the server side              #
    # of a many-clients <-> one-server              #
    # OpenVPN configuration.                        #
    #                                               #
    # OpenVPN also supports                         #
    # single-machine <-> single-machine             #
    # configurations (See the Examples page         #
    # on the web site for more info).               #
    #                                               #
    # This config should work on Windows            #
    # or Linux/BSD systems.  Remember on            #
    # Windows to quote pathnames and use            #
    # double backslashes, e.g.:                     #
    # "C:\\Program Files\\OpenVPN\\config\\foo.key" #
    #                                               #
    # Comments are preceded with '#' or ';'         #
    #################################################
    mode server
    # Which local IP address should OpenVPN
    # listen on? (optional)
    ;local a.b.c.d
    
    
    # Which TCP/UDP port should OpenVPN listen on?
    # If you want to run multiple OpenVPN instances
    # on the same machine, use a different port
    # number for each one.  You will need to
    # open up this port on your firewall.
    port 1723
    
    
    # TCP or UDP server?
    ;proto tcp
    proto udp
    
    
    # "dev tun" will create a routed IP tunnel,
    # "dev tap" will create an ethernet tunnel.
    # Use "dev tap0" if you are ethernet bridging
    # and have precreated a tap0 virtual interface
    # and bridged it with your ethernet interface.
    # If you want to control access policies
    # over the VPN, you must create firewall
    # rules for the the TUN/TAP interface.
    # On non-Windows systems, you can give
    # an explicit unit number, such as tun0.
    # On Windows, use "dev-node" for this.
    # On most systems, the VPN will not function
    # unless you partially or fully disable
    # the firewall for the TUN/TAP interface.
    dev tap0
    ;dev tun
    
    
    # script to attach the tap0 interface to the bridge
    up "/etc/openvpn/up.sh br0"
    down "/etc/openvpn/down.sh br0"
    
    
    # Windows needs the TAP-Win32 adapter name
    # from the Network Connections panel if you
    # have more than one.  On XP SP2 or higher,
    # you may need to selectively disable the
    # Windows firewall for the TAP adapter.
    # Non-Windows systems usually don't need this.
    ;dev-node MyTap
    
    
    # SSL/TLS root certificate (ca), certificate
    # (cert), and private key (key).  Each client
    # and the server must have their own cert and
    # key file.  The server and all clients will
    # use the same ca file.
    #
    # See the "easy-rsa" directory for a series
    # of scripts for generating RSA certificates
    # and private keys.  Remember to use
    # a unique Common Name for the server
    # and each of the client certificates.
    #
    # Any X509 key management system can be used.
    # OpenVPN can also use a PKCS #12 formatted key file
    # (see "pkcs12" directive in man page).
    ca ca.crt
    cert saturn.crt
    key saturn.key  # This file should be kept secret
    
    
    # Diffie hellman parameters.
    # Generate your own with:
    #   openssl dhparam -out dh1024.pem 1024
    # Substitute 2048 for 1024 if you are using
    # 2048 bit keys. 
    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
    
    
    # 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 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
    
    
    # Configure server mode for ethernet bridging
    # using a DHCP-proxy, where clients talk
    # to the OpenVPN server-side DHCP server
    # to receive their IP address allocation
    # and DNS server addresses.  You must first use
    # your OS's bridging capability to bridge the TAP
    # interface with the ethernet NIC interface.
    # Note: this mode only works on clients (such as
    # Windows), where the client-side TAP adapter is
    # bound to a DHCP client.
    ;server-bridge
    
    
    # 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 192.168.1.107 255.255.255.0"
    ;push "route 192.168.20.0 255.255.255.0"
    
    
    # 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
    # or bridge the TUN/TAP interface to the internet
    # in order for this to work properly).
    push "redirect-gateway def1"
    
    
    # Certain Windows-specific network settings
    # can be pushed to clients, such as DNS
    # or WINS server addresses.  CAVEAT:
    # http://openvpn.net/faq.html#dhcpcaveats
    # The addresses below refer to the public
    # DNS servers provided by opendns.com.
    push "dhcp-option DNS 192.168.1.1"
    push "dhcp-option WINS 192.168.1.1"
    ;push "dhcp-option DNS 208.67.220.220"
    
    
    # Uncomment this directive to allow different
    # clients to be able to "see" each other.
    # By default, clients will only see the server.
    # To force clients to only see the server, you
    # will also need to appropriately firewall the
    # server's TUN/TAP interface.
    client-to-client
    
    
    # Uncomment this directive if multiple clients
    # might connect with the same certificate/key
    # files or common names.  This is recommended
    # only for testing purposes.  For production use,
    # each client should have its own certificate/key
    # pair.
    #
    # IF YOU HAVE NOT GENERATED INDIVIDUAL
    # CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
    # EACH HAVING ITS OWN UNIQUE "COMMON NAME",
    # UNCOMMENT THIS LINE OUT.
    ;duplicate-cn
    
    
    # The keepalive directive causes ping-like
    # messages to be sent back and forth over
    # the link so that each side knows when
    # the other side has gone down.
    # Ping every 10 seconds, assume that remote
    # peer is down if no ping received during
    # a 120 second time period.
    keepalive 10 120
    
    
    # For extra security beyond that provided
    # by SSL/TLS, create an "HMAC firewall"
    # to help block DoS attacks and UDP port flooding.
    #
    # Generate with:
    #   openvpn --genkey --secret ta.key
    #
    # The server and each client must have
    # a copy of this key.
    # The second parameter should be '0'
    # on the server and '1' on the clients.
    ;tls-auth ta.key 0 # This file is secret
    
    
    # Select a cryptographic cipher.
    # This config item must be copied to
    # the client config file as well.
    ;cipher BF-CBC        # Blowfish (default)
    ;cipher AES-128-CBC   # AES
    ;cipher DES-EDE3-CBC  # Triple-DES
    
    
    # Enable compression on the VPN link.
    # If you enable it here, you must also
    # enable it in the client config file.
    comp-lzo
    
    
    # The maximum number of concurrently connected
    # clients we want to allow.
    max-clients 3
    
    
    # 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 nogroup
    
    
    # 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
    
    
    # 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).
    log         openvpn.log
    ;log-append  openvpn.log
    
    
    # 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
    
    
    script-security 3 system
    I've been reading various guides all day today and the server config came up a mixture of many of those, so I might have done something stupid there.

    Also, I am not entirely sure whether I have to use dev tap instead of dev tun, especially since I couldn't properly configure /etc/network/interfaces.

    Thanks again for your help!

  4. #4
    Join Date
    Aug 2013
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    Re: Configuring OpenVPN for internet access

    Hi,

    if all you want to do is get internet over the VPN Tunnel I would change from TAP and Bridging to TUN and routing.

    Server side config:
    Code:
    dev tun
    user nobody
    group nogroup
    port 1723
    ifconfig-pool-persist ipp.txt
    persist-tun
    persist-key
    server 10.8.0.0 255.255.255.0
    push "redirect-gateway def1"
    push "dhcp-option DNS IP_TO_DNS"
    ping-timer-rem
    keepalive 10 60
    comp-lzo
    dh dh2048.pem
    cert server.crt
    key server.key
    ca ca.crt
    Of course it should be doable with TAP but I find it easier to use TUN if all you want to do is get internet access from the client.

  5. #5
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    Dec 2009
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    Re: Configuring OpenVPN for internet access

    Thanks, mate! One more thing, please:

    In push "dhcp-option DNS IP_TO_DNS", which DNS should I use? The one from the ISP of the server, an open one (i.e. Google's 8.8.8.8) or...?

    P.S. Well, I followed your instructions and used Google's DNS. However, when I connect my Windows laptop, the vpn connection still shows as "Unidentified network - no internet access". Obviously Windows is indeed trying to route all traffic through that connection because I cannot open any website (Skype appears online, though), but nevertheless something is blocking my computer at the server, methinks.

    P.S2. I don't know if this is relevant, but the server (192.168.1.105) is behind a router (192.168.1.1).
    Last edited by zkvvoob; August 18th, 2013 at 10:48 AM.

  6. #6
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    Re: Configuring OpenVPN for internet access

    Quote Originally Posted by zkvvoob View Post
    Thanks, mate! One more thing, please:

    In push "dhcp-option DNS IP_TO_DNS", which DNS should I use? The one from the ISP of the server, an open one (i.e. Google's 8.8.8.8) or...?

    P.S. Well, I followed your instructions and used Google's DNS. However, when I connect my Windows laptop, the vpn connection still shows as "Unidentified network - no internet access". Obviously Windows is indeed trying to route all traffic through that connection because I cannot open any website (Skype appears online, though), but nevertheless something is blocking my computer at the server, methinks.

    P.S2. I don't know if this is relevant, but the server (192.168.1.105) is behind a router (192.168.1.1).
    Can you post the configuration you are using on the windows computer?

    Sometimes, mis-matched options (i.e. lzo enabled on server-side, lzo disabled on client-side will make a connection unusable)
    Ubuntu Forums Moderation Staff
    Don't waste your energy trying to change opinions ... Do your thing, and don't care if they like it.

  7. #7
    Join Date
    Dec 2009
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    Re: Configuring OpenVPN for internet access

    Quote Originally Posted by sandyd View Post
    Can you post the configuration you are using on the windows computer?

    Sometimes, mis-matched options (i.e. lzo enabled on server-side, lzo disabled on client-side will make a connection unusable)
    Certainly. Here's the client configuration:

    Code:
    ############################################### Sample client-side OpenVPN 2.0 config file #
    # for connecting to multi-client server.     #
    #                                            #
    # This configuration can be used by multiple #
    # clients, however each client should have   #
    # its own cert and key files.                #
    #                                            #
    # On Windows, you might want to rename this  #
    # file so it has a .ovpn extension           #
    ##############################################
    
    
    # Specify that we are a client and that we
    # will be pulling certain config file directives
    # from the server.
    client
    
    
    # Use the same setting as you are using on
    # the server.
    # On most systems, the VPN will not function
    # unless you partially or fully disable
    # the firewall for the TUN/TAP interface.
    ;dev tap
    dev tun
    
    
    # Windows needs the TAP-Win32 adapter name
    # from the Network Connections panel
    # if you have more than one.  On XP SP2,
    # you may need to disable the firewall
    # for the TAP adapter.
    ;dev-node MyTap
    
    
    # Are we connecting to a TCP or
    # UDP server?  Use the same setting as
    # on the server.
    ;proto tcp
    proto udp
    
    
    # The hostname/IP and port of the server.
    # You can have multiple remote entries
    # to load balance between the servers.
    remote ***.***.***.*** 1723
    ;remote my-server-2 1194
    
    
    # Choose a random host from the remote
    # list for load-balancing.  Otherwise
    # try hosts in the order specified.
    ;remote-random
    
    
    # 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
    
    
    # If you are connecting through an
    # HTTP proxy to reach the actual OpenVPN
    # server, put the proxy server/IP and
    # port number here.  See the man page
    # if your proxy server requires
    # authentication.
    ;http-proxy-retry # retry on connection failures
    ;http-proxy [proxy server] [proxy port #]
    
    
    # Wireless networks often produce a lot
    # of duplicate packets.  Set this flag
    # to silence duplicate packet warnings.
    ;mute-replay-warnings
    
    
    # SSL/TLS parms.
    # See the server config file for more
    # description.  It's best to use
    # a separate .crt/.key file pair
    # for each client.  A single ca
    # file can be used for all clients.
    ca ca.crt
    cert bz.crt
    key bz.key
    
    
    # Verify server certificate by checking
    # that the certicate has the nsCertType
    # field set to "server".  This is an
    # important precaution to protect against
    # a potential attack discussed here:
    #  http://openvpn.net/howto.html#mitm
    #
    # To use this feature, you will need to generate
    # your server certificates with the nsCertType
    # field set to "server".  The build-key-server
    # script in the easy-rsa folder will do this.
    ns-cert-type server
    
    
    # If a tls-auth key is used on the server
    # then every client must also have the key.
    ;tls-auth ta.key 1
    
    
    # Select a cryptographic cipher.
    # If the cipher option is used on the server
    # then you must also specify it here.
    ;cipher x
    
    
    # Enable compression on the VPN link.
    # Don't enable this unless it is also
    # enabled in the server config file.
    comp-lzo
    
    
    # Set log file verbosity.
    verb 3
    
    
    # Silence repeating messages
    ;mute 20
    
    
    route-metric 512 
    route 0.0.0.0 0.0.0.0
    I'd like to point out that I have no trouble connecting in general, the OpenVPN tray icon lights green and everything looks normal, except for the fact that I have no internet access and in the Windows Network and Sharing Center the VPN connection is marked as "Unidentified network".

  8. #8
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    Re: Configuring OpenVPN for internet access

    Use
    Code:
    iptables -t nat -A POSTROUTING -s 10.8.0.0/16 -o eth0 -j SNAT --to EXTERNAL_IP
    In your iptables, replacing EXTERNAL_IP with the ip of the outbound interface
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    Don't waste your energy trying to change opinions ... Do your thing, and don't care if they like it.

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