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I have configured my OpenVPN server as explained in this tutorial. After the configuration and setting everything up, I can connect my client to my server without a problem. However, after the connection is done I cannot access the internet from the client, nor can I connect anymore through ssh to the server through its public IP (I can ssh through the 10.8.0.1 vpn ip). Moreover, I can ssh any of the ehternet cards of the server (public and private 192.168.1...) but cannot ping or ssh any of the other computers on the private network of the server. I believe the problem is that after connecting to the server, I get no answer to the routes command.

Before connecting to vpn server:

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         _gateway        0.0.0.0         UG    20100  0        0 enp2s0
SERVERPUBLICIP  _gateway        255.255.255.255 UGH   0      0        0 enp2s0
192.168.8.0     0.0.0.0         255.255.255.0   U     100    0        0 enp2s0

After connecting to vpn server:

$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface

My server config file is:

#################################################
# 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 ';'         #
#################################################

# 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 PORTNUMBER 

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

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
dh dh.pem

# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet

# 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 /var/log/openvpn/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"
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
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
;push "redirect-gateway def1 bypass-dhcp"
push "redirect-gateway local 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 10.8.0.1"
push "dhcp-option DNS 192.168.1.1"
;push "dhcp-option DNS SERVERPUBLICIP"

# 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.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC
auth SHA256

# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
;compress lz4-v2
;push "compress lz4-v2"

# For compression compatible with older clients use comp-lzo
# 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 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 /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).
;log         /var/log/openvpn/openvpn.log
;log-append  /var/log/openvpn/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

# Notify the client that when the server restarts so it
# can automatically reconnect.
explicit-exit-notify 1 

in this file, PORTNUMBER and SERVERPUBLICIP are already set to my public IP and the port that is open on the router firewall.

My OpenVPN log (/var/log/openvpn/openvpn-status.log) says (after client connection):

OpenVPN CLIENT LIST
Updated,Wed Oct 16 08:25:13 2019
Common Name,Real Address,Bytes Received,Bytes Sent,Connected Since
apalomer,SOMEOTHERPUBLICIP:54864,13164,3569,Wed Oct 16 08:25:03 2019
ROUTING TABLE
Virtual Address,Common Name,Real Address,Last Ref
10.8.0.6,apalomer,SOMEOTHERPUBLICIP:54864,Wed Oct 16 08:25:12 2019
GLOBAL STATS
Max bcast/mcast queue length,1
END

Where SOMEOTHERPUBLICIP is not the public IP of the server.

The server network configuration is:

enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.108  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::e28f:a01d:c043:dc41  prefixlen 64  scopeid 0x20<link>
        ether e0:3f:49:47:95:8f  txqueuelen 1000  (Ethernet)
        RX packets 61664  bytes 4785172 (4.7 MB)
        RX errors 0  dropped 8818  overruns 0  frame 0
        TX packets 18200  bytes 1656024 (1.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp7s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet SERVERPUBLICIP  netmask 255.255.255.0  broadcast SERVERPUBLICIP.255
        inet6 fe80::9219:cc1d:57f5:ecc7  prefixlen 64  scopeid 0x20<link>
        ether e8:94:f6:02:85:4d  txqueuelen 1000  (Ethernet)
        RX packets 656236  bytes 511487988 (511.4 MB)
        RX errors 0  dropped 164  overruns 0  frame 0
        TX packets 187366  bytes 16304575 (16.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 126461  bytes 14656046 (14.6 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 126461  bytes 14656046 (14.6 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
        inet 10.8.0.1  netmask 255.255.255.255  destination 10.8.0.2
        inet6 fe80::d903:b10c:65b0:23fc  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 100  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 8  bytes 384 (384.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp4s0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 10:fe:ed:8c:25:3d  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

The client network configuration after connecting to the server is:

enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.8.4  netmask 255.255.255.0  broadcast 192.168.8.255
        inet6 fe80::e84e:bf84:9cf:7220  prefixlen 64  scopeid 0x20<link>
        ether 00:d8:61:31:40:72  txqueuelen 1000  (Ethernet)
        RX packets 431128  bytes 304709063 (304.7 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 326425  bytes 74418551 (74.4 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 50:3e:aa:0d:a1:3d  txqueuelen 1000  (Ethernet)
        RX packets 26793  bytes 4025965 (4.0 MB)
        RX errors 0  dropped 514  overruns 0  frame 0
        TX packets 6865  bytes 695724 (695.7 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 18262  bytes 1556456 (1.5 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 18262  bytes 1556456 (1.5 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
        inet 10.8.0.6  netmask 255.255.255.255  destination 10.8.0.5
        inet6 fe80::6c94:cddd:8cf5:e769  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 100  (UNSPEC)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 437  bytes 58238 (58.2 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp4s0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether f4:d1:08:d9:8e:65  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

With this configuration, I can ping 10.8.0.1(the server VPN IP) but not 192.168.1.108 (the server private network IP) neither the server public IP. I observe the same behavior if the changes suggested by kukulo in the comments (Replace the ip address in push "dhcp-option DNS 10.8.0.1" with your local dhcp ip address of your dhcp server and Replace push "redirect-gateway def1 bypass-dhcp" with push "redirect-gateway local def1")

In the server, ipv4 forwarding is on (from this section of the tutorial):

cat /proc/sys/net/ipv4/ip_forward
1

The server default route is:

$ ip route | grep default
default via 84.88.154.1 dev enp7s0 proto static metric 100 
default via 192.168.1.1 dev enp3s0 proto static metric 20101

The client default route is:

$ ip route | grep default
default via 192.168.8.254 dev enp2s0 proto dhcp metric 20106

The server /etc/default/ufw is:

# /etc/default/ufw
#

# Set to yes to apply rules to support IPv6 (no means only IPv6 on loopback
# accepted). You will need to 'disable' and then 'enable' the firewall for
# the changes to take affect.
IPV6=yes

# Set the default input policy to ACCEPT, DROP, or REJECT. Please note that if
# you change this you will most likely want to adjust your rules.
DEFAULT_INPUT_POLICY="DROP"

# Set the default output policy to ACCEPT, DROP, or REJECT. Please note that if
# you change this you will most likely want to adjust your rules.
DEFAULT_OUTPUT_POLICY="ACCEPT"

# Set the default forward policy to ACCEPT, DROP or REJECT.  Please note that
# if you change this you will most likely want to adjust your rules
DEFAULT_FORWARD_POLICY="ACCEPT"

# Set the default application policy to ACCEPT, DROP, REJECT or SKIP. Please
# note that setting this to ACCEPT may be a security risk. See 'man ufw' for
# details
DEFAULT_APPLICATION_POLICY="SKIP"

# By default, ufw only touches its own chains. Set this to 'yes' to have ufw
# manage the built-in chains too. Warning: setting this to 'yes' will break
# non-ufw managed firewall rules
MANAGE_BUILTINS=no

#
# IPT backend
#
# only enable if using iptables backend
IPT_SYSCTL=/etc/ufw/sysctl.conf

# Extra connection tracking modules to load. Complete list can be found in
# net/netfilter/Kconfig of your kernel source. Some common modules:
# nf_conntrack_irc, nf_nat_irc: DCC (Direct Client to Client) support
# nf_conntrack_netbios_ns: NetBIOS (samba) client support
# nf_conntrack_pptp, nf_nat_pptp: PPTP over stateful firewall/NAT
# nf_conntrack_ftp, nf_nat_ftp: active FTP support
# nf_conntrack_tftp, nf_nat_tftp: TFTP support (server side)
# nf_conntrack_sane: sane support
IPT_MODULES="nf_conntrack_ftp nf_nat_ftp nf_conntrack_netbios_ns"

The content of the server's /etc/ufw/before.rules is:

#
# rules.before
#
# Rules that should be run before the ufw command line added rules. Custom
# rules should be added to one of these chains:
#   ufw-before-input
#   ufw-before-output
#   ufw-before-forward
#

# START OPENVPN RULES
# NAT table rules
*nat
#:POSTROUTING ACCEPT [0:0] 
# Allow traffic from OpenVPN client to wlp11s0 (change to the interface you discovered!)
-A POSTROUTING -s 10.8.0.0/8 -o enp3s0 -j MASQUERADE
COMMIT
# END OPENVPN RULES

# Don't delete these required lines, otherwise there will be errors
*filter
:ufw-before-input - [0:0]
:ufw-before-output - [0:0]
:ufw-before-forward - [0:0]
:ufw-not-local - [0:0]
# End required lines


# allow all on loopback
-A ufw-before-input -i lo -j ACCEPT
-A ufw-before-output -o lo -j ACCEPT

# quickly process packets for which we already have a connection
-A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
-A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

# drop INVALID packets (logs these in loglevel medium and higher)
-A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny
-A ufw-before-input -m conntrack --ctstate INVALID -j DROP

# ok icmp codes for INPUT
-A ufw-before-input -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-input -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-input -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT

# ok icmp code for FORWARD
-A ufw-before-forward -p icmp --icmp-type destination-unreachable -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type time-exceeded -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type parameter-problem -j ACCEPT
-A ufw-before-forward -p icmp --icmp-type echo-request -j ACCEPT

# allow dhcp client to work
-A ufw-before-input -p udp --sport 67 --dport 68 -j ACCEPT

#
# ufw-not-local
#
-A ufw-before-input -j ufw-not-local

# if LOCAL, RETURN
-A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN

# if MULTICAST, RETURN
-A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN

# if BROADCAST, RETURN
-A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN

# all other non-local packets are dropped
-A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny
-A ufw-not-local -j DROP

# allow MULTICAST mDNS for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT

# allow MULTICAST UPnP for service discovery (be sure the MULTICAST line above
# is uncommented)
-A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT

# don't delete the 'COMMIT' line or these rules won't be processed
COMMIT

Any ideas on what can I do?

I've tried:

| improve this question | | | | |
  • Looks like the routes do not exist between the openvpn and rest of the world. What is your server openvpn.conf file? – kukulo Oct 15 '19 at 15:16
  • I've added it to the question. – apalomer Oct 15 '19 at 15:31
  • What does your openvpn.log file says when the client is connected? – kukulo Oct 15 '19 at 17:23
  • Replace the ip address in push "dhcp-option DNS 10.8.0.1" with your local dhcp ip address of your dhcp server, usually gateway. – kukulo Oct 15 '19 at 17:27
  • Replace push "redirect-gateway def1 bypass-dhcp" with push "redirect-gateway local def1". – kukulo Oct 15 '19 at 17:27
0
  1. Check your default route:

    ip route | grep default
    
  2. Output

    default via 84.88.154.1 dev enp7s0 proto static metric 100 
    default via 192.168.1.1 dev enp3s0 proto static metric 20101
    

    When enp3s0 is your default output interface for internal network, then

  3. Command:

    sudo nano /etc/ufw/before.rules
    
  4. Edit the before.rules file:

/etc/ufw/before.rules:

#
# rules.before
#
# Rules that should be run before the ufw command line added rules. Custom
# rules should be added to one of these chains:
#   ufw-before-input
#   ufw-before-output
#   ufw-before-forward
#

# START OPENVPN RULES
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0] 
# Allow traffic from OpenVPN client to enp3s0 (change to the interface you discovered!)
-A POSTROUTING -s 10.8.0.0/8 -o enp3s0 -j MASQUERADE
COMMIT
# END OPENVPN RULES

# Don't delete these required lines, otherwise there will be errors
*filter
. . .
  1. Command:

    sudo nano /etc/default/ufw
    
  2. Change: /etc/default/ufw:

    DEFAULT_FORWARD_POLICY="ACCEPT"
    
  3. Commands:

    sudo ufw disable
    
    sudo ufw enable
    
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  • should all that be done on the server or the client? – apalomer Oct 16 '19 at 15:48
  • This should be done on server. – kukulo Oct 16 '19 at 15:54
  • I have updated the answer with your correct interface enp3s0. – kukulo Oct 16 '19 at 16:45
  • I've done these changes and it still does not work. I will redo the entire tutorial from scratch to see what have I done wrong. – apalomer Oct 17 '19 at 6:49
  • This is the missing command: -A POSTROUTING -s 10.8.0.0/8 -o enp3s0 -j MASQUERADE – kukulo Oct 18 '19 at 17:48
0

The actual correct answer is that you have the redirect-gateway option specified.

See first answer here: https://serverfault.com/questions/480069/how-to-force-all-traffic-through-vpn

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  • After changing this I have internet access, but I do not have access to the other networks of the server although I can ping the server card on the local network (192.168.1....) that is not the one that I used for connecting the VPN – apalomer Oct 17 '19 at 6:42
0

I figured it out. The problem was in the NAT of the iptables:

sudo iptables -t nat -L --line-numbers
Chain PREROUTING (policy ACCEPT)
num  target     prot opt source               destination         

Chain INPUT (policy ACCEPT)
num  target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
num  target     prot opt source               destination         

Chain POSTROUTING (policy ACCEPT)
num  target     prot opt source               destination         
1    MASQUERADE  all  --  10.8.0.0/24          anywhere            
2    SNAT       all  --  10.8.0.0/24         !10.8.0.0/24          to:84.88.154.241

POSTROUTING number 2 needs to be deleted:

sudo iptables -t nat -D POSTROUTING 2

However, this only fixes the problem until the system is rebooted. After reboot, this line is again in the iptables and needs to be removed again.

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