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I have problems with routing ALL windows traffic thorough OpenVPN tunnel and tried to solve this issue for hours. However, most advices about it did not help in my situation.

I have OpenVPN successfully installed in two Windows machines. Server and client networks are connected by static routes and can successfully ping each other. The Windows firewalls are off. The connection is successfully established (I can see it from OpenVPN GUI).

The problem is in routing ALL the traffic though OpenVPN tunnel. When I try to access a server (not OpenVPN server, just a server in another network that I use for testing connectivity) from VPN client it is possible to see though Wireshark on client's side that traffic doesn't go through OpenVPN server, it just goes straightforwardly to the desired server. So, in wireshark it looks this way:

192.168.3.10 - 192.168.4.10 HTTP
192.168.4.10 - 192.168.3.10 HTTP

As I understand if I capture from physical interface of the client I should see traffic being sent not to desired server (192.168.4.10) from physical interface ip (192.168.3.10), but to VPN server (10.8.0.1). So, this output probably means that routing doesn't work as it should. In the vpn interface of the client I see only llmnr packets, which probably means that the tunnel is not used for real traffic.

I can successfully ping from VPN server to client and opposite way thought the VPN tunnel.

I have tried advises to add push "redirect-gateway def1" and to server, to replace it with just redirect-gateway def1. Also i tried to add this to the client's config but it didn't work either. Also I used the official OpenVPN guide on this issue but it did not help either.

My server configuration looks this way:

# 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 1194

# 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 tap
dev tun

# 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 "C:\\Program Files (x86)\\OpenVPN\\config\\ca.crt"
cert "C:\\Program Files (x86)\\OpenVPN\\config\\server.crt"
key "C:\\Program Files (x86)\\OpenVPN\\config\\server.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 dh2048.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 192.168.10.0 255.255.255.0"
;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 bypass-dhcp"
;push "dhcp-option DNS 10.8.0.1"

# 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 208.67.222.222"
;push "dhcp-option DNS 208.67.220.220"
;push "dhcp-option DNS 10.8.0.1"


# 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 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

# 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

Here is client's configuration:

# 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 192.168.2.10 1194
#;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 "C:\\Program Files (x86)\\OpenVPN\\config\\ca.crt"
cert "C:\\Program Files (x86)\\OpenVPN\\config\\client2.crt"
key "C:\\Program Files (x86)\\OpenVPN\\config\\client2.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

;redirect-gateway def1

After client is connected it shows this log which looks like the route was successfully set up:

Tue Aug 11 13:12:48 2015 OpenVPN 2.1.3 i686-pc-mingw32 [SSL] [LZO2] [PKCS11] built on Aug 20 2010
Tue Aug 11 13:12:48 2015 NOTE: OpenVPN 2.1 requires '--script-security 2' or higher to call user-defined scripts or executables
Tue Aug 11 13:12:48 2015 LZO compression initialized
Tue Aug 11 13:12:48 2015 Control Channel MTU parms [ L:1542 D:138 EF:38 EB:0 ET:0 EL:0 ]
Tue Aug 11 13:12:48 2015 Socket Buffers: R=[65536->65536] S=[65536->65536]
Tue Aug 11 13:12:48 2015 Data Channel MTU parms [ L:1542 D:1450 EF:42 EB:135 ET:0 EL:0 AF:3/1 ]
Tue Aug 11 13:12:48 2015 Local Options hash (VER=V4): '41690919'
Tue Aug 11 13:12:48 2015 Expected Remote Options hash (VER=V4): '530fdded'
Tue Aug 11 13:12:48 2015 UDPv4 link local: [undef]
Tue Aug 11 13:12:48 2015 UDPv4 link remote: 192.168.2.10:1194
Tue Aug 11 13:12:48 2015 TLS: Initial packet from 192.168.2.10:1194, sid=6a402021 851404f4
Tue Aug 11 13:12:48 2015 VERIFY OK: depth=1, /C=FI/ST=CA/L=Mikkeli/O=OpenVPN-CA/OU=MyOrganizationalUnit/CN=OpanVPN-CA/name=EasyRSA/emailAddress=me@myhost.mydomain
Tue Aug 11 13:12:48 2015 VERIFY OK: nsCertType=SERVER
Tue Aug 11 13:12:48 2015 VERIFY OK: depth=0, /C=FI/ST=CA/L=Mikkeli/O=OpenVPN-CA/OU=MyOrganizationalUnit/CN=server/name=EasyRSA/emailAddress=me@myhost.mydomain
Tue Aug 11 13:12:49 2015 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
Tue Aug 11 13:12:49 2015 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Tue Aug 11 13:12:49 2015 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
Tue Aug 11 13:12:49 2015 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
Tue Aug 11 13:12:49 2015 Control Channel: TLSv1, cipher TLSv1/SSLv3 DHE-RSA-AES256-SHA, 2048 bit RSA
Tue Aug 11 13:12:49 2015 [server] Peer Connection Initiated with 192.168.2.10:1194
Tue Aug 11 13:12:52 2015 SENT CONTROL [server]: 'PUSH_REQUEST' (status=1)
Tue Aug 11 13:12:52 2015 PUSH: Received control message: 'PUSH_REPLY,route 10.8.0.1,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5'
Tue Aug 11 13:12:52 2015 OPTIONS IMPORT: timers and/or timeouts modified
Tue Aug 11 13:12:52 2015 OPTIONS IMPORT: --ifconfig/up options modified
Tue Aug 11 13:12:52 2015 OPTIONS IMPORT: route options modified
Tue Aug 11 13:12:52 2015 ROUTE default_gateway=192.168.3.1
Tue Aug 11 13:12:52 2015 TAP-WIN32 device [Local Area Connection 2] opened: \\.\Global\{DA7613B2-C24F-408D-B0D7-829D07CFC698}.tap
Tue Aug 11 13:12:52 2015 TAP-Win32 Driver Version 9.7 
Tue Aug 11 13:12:52 2015 TAP-Win32 MTU=1500
Tue Aug 11 13:12:52 2015 Notified TAP-Win32 driver to set a DHCP IP/netmask of 10.8.0.6/255.255.255.252 on interface {DA7613B2-C24F-408D-B0D7-829D07CFC698} [DHCP-serv: 10.8.0.5, lease-time: 31536000]
Tue Aug 11 13:12:52 2015 Successful ARP Flush on interface [29] {DA7613B2-C24F-408D-B0D7-829D07CFC698}
Tue Aug 11 13:12:57 2015 TEST ROUTES: 1/1 succeeded len=1 ret=1 a=0 u/d=up
Tue Aug 11 13:12:57 2015 C:\WINDOWS\system32\route.exe ADD 10.8.0.1 MASK 255.255.255.255 10.8.0.5
Tue Aug 11 13:12:57 2015 ROUTE: CreateIpForwardEntry succeeded with dwForwardMetric1=30 and dwForwardType=4
Tue Aug 11 13:12:57 2015 Route addition via IPAPI succeeded [adaptive]
Tue Aug 11 13:12:57 2015 Initialization Sequence Completed

And this is the routing table of the client PC:

C:\Windows\System32>route print
===========================================================================
Interface List
 29...00 ff da 76 13 b2 ......TAP-Win32 Adapter V9
 12...f8 1a 67 04 6a cb ......Realtek PCI GBE Family Controller
  1...........................Software Loopback Interface 1
 17...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2
 16...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
===========================================================================

IPv4 Route Table
===========================================================================
Active Routes:
Network Destination        Netmask          Gateway       Interface  Metric
          0.0.0.0          0.0.0.0      192.168.3.1     192.168.3.10    276
         10.8.0.1  255.255.255.255         10.8.0.5         10.8.0.6     30
         10.8.0.4  255.255.255.252         On-link          10.8.0.6    286
         10.8.0.6  255.255.255.255         On-link          10.8.0.6    286
         10.8.0.7  255.255.255.255         On-link          10.8.0.6    286
        127.0.0.0        255.0.0.0         On-link         127.0.0.1    306
        127.0.0.1  255.255.255.255         On-link         127.0.0.1    306
  127.255.255.255  255.255.255.255         On-link         127.0.0.1    306
      192.168.3.0    255.255.255.0         On-link      192.168.3.10    276
     192.168.3.10  255.255.255.255         On-link      192.168.3.10    276
    192.168.3.255  255.255.255.255         On-link      192.168.3.10    276
        224.0.0.0        240.0.0.0         On-link         127.0.0.1    306
        224.0.0.0        240.0.0.0         On-link          10.8.0.6    286
        224.0.0.0        240.0.0.0         On-link      192.168.3.10    276
  255.255.255.255  255.255.255.255         On-link         127.0.0.1    306
  255.255.255.255  255.255.255.255         On-link          10.8.0.6    286
  255.255.255.255  255.255.255.255         On-link      192.168.3.10    276
===========================================================================
Persistent Routes:
  Network Address          Netmask  Gateway Address  Metric
          0.0.0.0          0.0.0.0      192.168.3.1  Default
===========================================================================

IPv6 Route Table
===========================================================================
Active Routes:
 If Metric Network Destination      Gateway
 12    276 ::/0                     2001:a1b1:442e:1323::9
  1    306 ::1/128                  On-link
 12    276 2001:a1b1:442e:1323::/64 On-link
 12    276 2001:a1b1:442e:1323::4/128
                                    On-link
 29    286 fe80::/64                On-link
 12    276 fe80::/64                On-link
 29    286 fe80::8df8:71fc:fc47:ccf3/128
                                    On-link
 12    276 fe80::90c7:c659:f96c:781d/128
                                    On-link
  1    306 ff00::/8                 On-link
 29    286 ff00::/8                 On-link
 12    276 ff00::/8                 On-link
===========================================================================
Persistent Routes:
 If Metric Network Destination      Gateway
  0 4294967295 ::/0                     2001:a1b1:442e:1323::9
===========================================================================

I will be very thankful for your help

  • Once connected to the VPN can you show what is the routing table of the client and the IP of the server you are connecting to? – Alex Aug 10 '15 at 16:49
  • Any additions / modifications / etc of the routing table in Windows requires administrator privileges. Make sure you "Run as administrator" the OpenVPN client so it can do so. – Brian Aug 10 '15 at 18:02
  • @Brian Yes, I always run it as administrator – OrangeJuice Aug 11 '15 at 10:31
  • @Alex I undated the question and added logs – OrangeJuice Aug 11 '15 at 11:06
0

Your routing is fine.

The server is the destination because you are looking at the IP header.

You have to look at the Ethernet frame header to see the routing towards your gateway.

Obviously, you won't see IPs there, what you will see is that the destination of your packet is the MAC address of your gateway (192.168.3.1).


Unfortunately it's impossible to "sniff" VPN packets with Wireshark on Windows.

This doesn't mean you cannot see that packets that you are sending in the VPN tunnel, you just don't see the encapsulating part of these packets that allow them to transit within the VPN tunnel and get encrypted.

This also leads to the second part of your comment.

The reason why you don't see your data as encrypted is simply because you are not sniffing the traffic as it leaves your interface physically. You are sniffing the traffic as it leaves your internal interface and before it's sent to the virtual interface that OpenVPN created.

  • Yes, you are correct about the Ethernet header and it indeed leads to the MAC of the gateway. But that is where I have the problem. I know that the packets go to that gateway of physical interface and then straightaway to the 192.168.4.0 network to the server. If the vpn works correctly it should be other way, right? It should go to 10.8.0.5 gateway, then to openvpn server and only after that to the 192.168.4.0 network. In addition to that I can see that HTTP requests are not encrypted, but they should leave the physical interface in encrypted form, so something is wrong. – OrangeJuice Aug 11 '15 at 14:01
  • Hmm, when I access web-server on OpenVPN server I use Wireshark in both interfaces. Physical interface shows many packets of protocol "OPENVPN" and type "P_DATA_V1". Tutorial says that this is ciphertext which means that I actually see the encrypted data. Virtual interface shows many HTTP requests, e.g. unencrypted data. So i disagree that Wireshark won't work, it is working correct in my case - virtual interface unencrypted, and physical one encrypted. Problem is that the same doesn't happen with other servers. – OrangeJuice Aug 11 '15 at 16:01

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