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megloff
Asked: 2016-11-04 12:42:26 +0800 CST

OpenVPN - Linux client could not access internet, routing issue

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I installed OpenVPN server quite a while a go with the gateway option that all internet traffic get routed through.

It works fine for client machine like Windows and my Android phone, but same Open VPN client config on my Ubuntu notebook seems not to work. client connects but internet traffic seems not to get routed.

Pinging the server does work: ping 10.8.0.1

so not sure what is missing. I tried so far the following options

  • added to client a route config: route 10.8.0.0/24
  • added via console a route config: sudo route add -net 10.8.0.0/24 gw 10.8.0.1 dev tun0
  • turned off firewall on client

Any help or hints are appreciated. Thanks

server config:

port 443
proto tcp
dev tun
ca ...
cert ...
key ...
dh ...
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1 bypasss-dhcp"
push "dhcp-option DNS 8.8.8.8"
push "dhcp-option DNS 8.8.4.4"
client-to-client
keepalive 10 120
comp-lzo
persist-key
persist-tun
status ...
log ...
verb 3

client config:

client
dev tun
proto tcp
remote www.serverdomain.com 443
resolv-retry infinite
nobind
persist-key
persist-tun
comp-lzo
verb 3
remote-cert-tls server
# route 10.8.0.0/24 --> adding such a route made no difference

client ifconfig:

tun0      
      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
      inet addr:10.8.0.10  P-t-P:10.8.0.9  Mask:255.255.255.255
      inet6 addr: fe80::b393:268c:61db:72d4/64 Scope:Link
      UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
      RX packets:47 errors:0 dropped:0 overruns:0 frame:0
      TX packets:93 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:100 
      RX bytes:4394 (4.3 KB)  TX bytes:7012 (7.0 KB)

wlp1s0    
      Link encap:Ethernet  HWaddr a4:34:d9:5c:9d:06  
      inet addr:192.168.0.130  Bcast:192.168.0.255  Mask:255.255.255.0
      inet6 addr: fe80::5e97:3a8f:9596:8c30/64 Scope:Link
      UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
      RX packets:24879 errors:0 dropped:0 overruns:0 frame:0
      TX packets:17473 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:14983497 (14.9 MB)  TX bytes:2721828 (2.7 MB)

client log output:

 Thu Nov  3 21:03:25 2016 OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Feb  2 2016
 Thu Nov  3 21:03:25 2016 library versions: OpenSSL 1.0.2g-fips  1 Mar 2016, LZO 2.08
 Thu Nov  3 21:03:25 2016 Socket Buffers: R=[87380->87380] S=[16384->16384]
 Thu Nov  3 21:03:25 2016 Attempting to establish TCP connection with [AF_INET]188.62.xx.xx:443 [nonblock]
 Thu Nov  3 21:03:26 2016 TCP connection established with [AF_INET]188.62.xx.xx:443
 Thu Nov  3 21:03:26 2016 TCPv4_CLIENT link local: [undef]
 Thu Nov  3 21:03:26 2016 TCPv4_CLIENT link remote: [AF_INET]188.62.xx.xx:443
 Thu Nov  3 21:03:26 2016 TLS: Initial packet from [AF_INET]188.62.xx.xx:443, sid=ff1258e5 f87eeaf5
 Thu Nov  3 21:03:26 2016 VERIFY OK: depth=1, C=CH, ST=ZH, L=Hinwil, O=xxx, OU=IT, CN=xxxx, name=xxxx, emailAddress=xxxx.ch
 Thu Nov  3 21:03:26 2016 Validating certificate key usage
 Thu Nov  3 21:03:26 2016 ++ Certificate has key usage  00a0, expects 00a0
 Thu Nov  3 21:03:26 2016 VERIFY KU OK
 Thu Nov  3 21:03:26 2016 Validating certificate extended key usage
 Thu Nov  3 21:03:26 2016 ++ Certificate has EKU (str) TLS Web Server Authentication, expects TLS Web Server Authentication
 Thu Nov  3 21:03:26 2016 VERIFY EKU OK
 Thu Nov  3 21:03:26 2016 VERIFY OK: depth=0, C=CH, ST=ZH, L=Hinwil, O=xxxx, OU=IT, CN=xxxx, name=xxxxx, emailAddress=xxxx.ch
 Thu Nov  3 21:03:26 2016 Data Channel Encrypt: Cipher 'BF-CBC' initialized with 128 bit key
 Thu Nov  3 21:03:26 2016 Data Channel Encrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
 Thu Nov  3 21:03:26 2016 Data Channel Decrypt: Cipher 'BF-CBC' initialized with 128 bit key
 Thu Nov  3 21:03:26 2016 Data Channel Decrypt: Using 160 bit message hash 'SHA1' for HMAC authentication
 Thu Nov  3 21:03:26 2016 Control Channel: TLSv1.2, cipher     TLSv1/SSLv3 DHE-RSA-AES256-GCM-SHA384, 2048 bit RSA
 Thu Nov  3 21:03:26 2016 [xxxx] Peer Connection Initiated with [AF_INET]188.62.xx.xx:443
 Thu Nov  3 21:03:28 2016 SENT CONTROL [diabolo]: 'PUSH_REQUEST' (status=1)
 Thu Nov  3 21:03:29 2016 PUSH: Received control message: 'PUSH_REPLY,redirect-gateway def1 bypass-dhcp,dhcp-option DNS 8.8.8.8,dhcp-option DNS 8.8.4.4,route 10.8.0.0 255.255.255.0,topology net30,ping 10,ping-restart 120,ifconfig 10.8.0.6 10.8.0.5'
 Thu Nov  3 21:03:29 2016 OPTIONS IMPORT: timers and/or timeouts modified
 Thu Nov  3 21:03:29 2016 OPTIONS IMPORT: --ifconfig/up options modified
 Thu Nov  3 21:03:29 2016 OPTIONS IMPORT: route options modified
 Thu Nov  3 21:03:29 2016 OPTIONS IMPORT: --ip-win32 and/or --dhcp-option options modified
 Thu Nov  3 21:03:29 2016 ROUTE_GATEWAY 192.168.0.1/255.255.255.0 IFACE=wlp1s0 HWADDR=a4:34:d9:5c:9d:06
 Thu Nov  3 21:03:29 2016 TUN/TAP device tun0 opened
 Thu Nov  3 21:03:29 2016 TUN/TAP TX queue length set to 100
 Thu Nov  3 21:03:29 2016 do_ifconfig, tt->ipv6=0, tt->did_ifconfig_ipv6_setup=0
 Thu Nov  3 21:03:29 2016 /sbin/ip link set dev tun0 up mtu 1500
 Thu Nov  3 21:03:29 2016 /sbin/ip addr add dev tun0 local 10.8.0.6 peer 10.8.0.5
 Thu Nov  3 21:03:29 2016 /sbin/ip route add 188.62.79.43/32 via 192.168.0.1
 Thu Nov  3 21:03:29 2016 /sbin/ip route add 0.0.0.0/1 via 10.8.0.5
 Thu Nov  3 21:03:29 2016 /sbin/ip route add 128.0.0.0/1 via 10.8.0.5
 Thu Nov  3 21:03:29 2016 /sbin/ip route add 10.8.0.0/24 via 10.8.0.5
 Thu Nov  3 21:03:29 2016 Initialization Sequence Completed

client netstat -rn

 Kernel IP routing table
 Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
 0.0.0.0         10.8.0.9        128.0.0.0       UG        0 0          0 tun0
 0.0.0.0         192.168.0.1     0.0.0.0         UG        0 0          0 wlp1s0
 10.8.0.0        10.8.0.9        255.255.255.0   UG        0 0          0 tun0
 10.8.0.9        0.0.0.0         255.255.255.255 UH        0 0          0 tun0
 128.0.0.0       10.8.0.9        128.0.0.0       UG        0 0          0 tun0
 169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 wlp1s0
 188.62.xx.xx    192.168.0.1     255.255.255.255 UGH       0 0          0 wlp1s0
 192.168.0.0     0.0.0.0         255.255.255.0   U         0 0          0 wlp1s0
networking

1 Answers

  1. Best Answer

    I could solve the issue by lowering the "metrics" of my ethernet/wifi card. you can lower the metrics (priority) of the routing entries for your network card via the "route" command or by using the additional tool "ifmetric" (sudo apt-get install ifmetric) i.e. ifmetric eth0 100 (0 = highest priority)

    After that I recognized that the DNS entries from the openvpn server has not been taken over when vpn connection has been setup. so I googled around and I found an answer that you need to add on the ubuntu client the following lines on its config file:

    script-security 2
up /etc/openvpn/update-resolv-conf
down /etc/openvpn/update-resolv-conf

    This updates the DNS entries in the /etc/resolv.conf when the vpn connection is established by using the pushed entries from the server.

    So it works now like a charm.

    UPDATE: I had as well to install the package "resolvconf" (sudo apt-get install resolvconf) otherwise the script "/etc/openvpn/update-resolv-conf" will not work and "/etc/resolv.conf" will not be updated with the nameserver

    • 4