Question

OpenVPN - IPv6 works only in local network

  • Posted January 2, 2015

Hello everyone,

I have dual stack OpenVPN server:

IPv4 works fine, but IPv6 works only in local network. I would like to access the IPv6 Internet through my VPN.

Server eth0 IP: 2a03:b0c0:1:d0::7f:8001/64 Server tun0 IP: 2a03:b0c0:1:d0::7f:8002/64 Client tun0 IP: 2a03:b0c0:1:d0::7f:8003/64

Server

ip6tables

Chain INPUT (policy DROP 240 packets, 19200 bytes)
 pkts bytes target     prot opt in     out     source               destination         
   32  6574 ACCEPT     all      lo     *       ::/0                 ::/0                
  167 14920 ACCEPT     icmpv6   *      *       ::/0                 ::/0                
   36  3242 ACCEPT     udp      *      *       ::/0                 ::/0                 udp dpt:53
    6   481 ACCEPT     tcp      *      *       ::/0                 ::/0                 tcp dpt:53
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0                 tcp dpt:22
    0     0 ACCEPT     tcp      *      *       ::/0                 ::/0                 tcp dpt:1194
  246 28608 ACCEPT     all      *      *       ::/0                 ::/0                 state RELATED,ESTABLISHED

Chain FORWARD (policy ACCEPT 15 packets, 1560 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 569 packets, 91798 bytes)
 pkts bytes target     prot opt in     out     source               destination  

server.conf

mode server
tls-server
proto tcp-server
dev tun0
tun-ipv6
topology subnet

client-to-client
ifconfig 192.168.192.1 255.255.255.0
ifconfig-ipv6 2a03:b0c0:1:d0::7f:8002 2a03:b0c0:1:d0::7f:8001
client-config-dir /etc/openvpn/ccd

ccd/client

ifconfig-push 192.168.192.3 255.255.255.0 # vps
ifconfig-ipv6-push 2a03:b0c0:1:d0::7f:8003/64

push "route-ipv6 2a03:b0c0:1:d0::7f:8001/64"
push "route-ipv6 2000::/3"

sysctl.conf

net.ipv6.conf.all.forwarding=1

Client

client.conf

remote shark.pdostal.cz 1194
proto tcp
tls-client
dev tun1
tun-ipv6
proto tcp-client
remote-cert-tls server

pull

Both server & client configs

<certificates>

keepalive 10 30

comp-lzo
persist-key
persist-tun

verb 2

Do you have any idea what is wrong? Thanks you for your help!

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Ok let me know if you can make ipv6 work.

I’m still testing and as I said, local network works normally.

So what’s your plan ? Just waiting help or testing some stuff ?

Yes, client receives address and routes properly. Also connection in local network works normally. Only connection to the Internet is broken.

Within a tcpdump look if you have neighbor solicitation asking on the client IP.


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In CCD do

iroute-ipv6 2a03:b0c0:1:d0::7f:8001/64 iroute-ipv6 2000::/3

instead of push “route-ipv6 2a03:b0c0:1:d0::7f:8001/64” push “route-ipv6 2000::/3”

This comment has been deleted

Okay, I solved this problem. Tested on clean OpenVPN installed by that tutorial: https://www.digitalocean.com/community/tutorials/how-to-set-up-an-openvpn-server-on-ubuntu-14-04

We need to create another subnet(?) for OpenVPN, so in /etc/openvpn/server.conf add: server-ipv6 ANY_IP_V6::/112

I used my server IP replacing two colons in it for one and adding at the end :80::/112

Now create rule: ip6tables -t nat -A POSTROUTING -s YOUR_ANY_IP_V6/112 -j SNAT --to YOUR_SERVER_IP

And remember, in /etc/sysctl.conf uncomment: net.ipv6.conf.all.forwarding = 1

Restart, reconnect and check test-ipv6.com. This site shows problem with big MTU, but I don’t know now how to solve it

BTW sorry for my bad english.

Anyone solved this problem?