I have OpenVPN installed on my Ubuntu 14.04 VPS with IPv6 access. I would like to have a proper dual stack configuration working. I can connect to my OpenVPN server's public IPv4 address: get private IPv4 and public IPv6 assigned to me, and have full IPv4 and IPv6 connectivity working through the VPN (checked with test-ipv6.com).

Problem is, if I connect to the server's IPv6 address (I have IPv6 on my ISP connection), I am able to successfully connect to it and get IPv4 and IPv6 addresses assigned but unable to get any sort of connectivity going, not even ping to any internal or external IP or host including the server's private IPv4 address in the tunnel. I have enabled IPv4 and IPv6 forwarding in /etc/sysctl.conf.

I am unsure what is going on. Help is very much appreciated.

Thank you.

IP info (masked):

  • VPS IPv4 address (device: eth0): 107.xxx.xxx.xxx
  • VPS IPv6 subnet (device: he-ipv6): 2001:xxx:xxxx::/48
  • OpenVPN IPv4 subnet:
  • OpenVPN IPv4 private address:
  • OpenVPN IPv4 client addresses:,, [...]
  • OpenVPN IPv6 subnet: 2001:xxx:xxxx:xxx::/64
  • OpenVPN IPv6 server address: 2001:xxx:xxxx:xxx::1/64
  • OpenVPN IPv6 client addresses: 2001:xxx:xxxx:xxx::1000/64, 2001:xxx:xxxx:xxx::1001/64, [...]

/etc/openvpn/server.conf contents:

port 443
proto tcp6
dev tun
sndbuf 0
rcvbuf 0
ca ca.crt
cert server.crt
key server.key
dh dh.pem
tls-auth ta.key 0
topology subnet
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS"
push "dhcp-option DNS"
keepalive 10 120
cipher AES-128-CBC
user nobody
group nogroup
status openvpn-status.log
verb 3
crl-verify crl.pem
push tun-ipv6
server-ipv6 2001:xxx:xxxx:xxx::/64
push "redirect-gateway-ipv6 def1 bypass-dhcp-ipv6"
push "route-ipv6 2001:xxx:xxxx:xxx::/64"
push "route-ipv6 2000::/3"

client.ovpn contents:

dev tun
sndbuf 0
rcvbuf 0
;remote 107.xxx.xxx.xxx 443 tcp # IPv4 (disabled; full IPv4 and IPv6 connectivity when connected)
remote 2001:xxx:xxxx:xxx::1 443 tcp6 # IPv6 (enabled; no connectivity when connected)
resolv-retry infinite
remote-cert-tls server
cipher AES-128-CBC
setenv opt block-outside-dns
key-direction 1
verb 3

1 Answer 1


I managed to solve this issue by using the latest alpha of OpenVPN 2.4 (alpha2) on the client computer (running Ubuntu 16.04; had to manually compile and install OpenVPN), after I realised I can connect over IPv6 on my Android phone using the 'OpenVPN for Android' application, which is running the same 2.4 version. I was running version 2.3.10.


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