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I have set up 2 VPN servers in 2 different locations (A running strongswan as server and openvpn as client; B running openvpn as server), And A and B is linked via openvpn. What I want to do is to make A route all client traffic to port 443 and 80 through the openvpn tunnel established between A and B.

I have added a routing table which will route all marked traffic (-t mangle PREROUTING -p tcp -m tcp --dport 443 -j MARK --set-xmark 0x2/0xffffffff) to the openvpn tunnel

I can see the marked traffic is successfully routed to the tunnel using tcpdump (tcpdump -i tun0) but there is only outgoing traffic and no incoming traffic.

Hope someone can help me with this. Thank you!

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  • Does B have a route back to the client IP addresses via A? May 24, 2015 at 13:50
  • @roaima, B have no specific route to client ip. How can i do this?
    – JIA
    May 24, 2015 at 14:05

1 Answer 1

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The problem here is that although clients of A (let's call them X, Y, Z) can route to B via your VPN link, there is no route from B back to clients X, Y, Z.

Without specifics it's tricky to provide an exact solution. Consider this example, though:

  1. Your clients are in subnet 192.168.1.0/24
  2. Server A has its end of the OpenVPN link as 192.168.2.1
  3. Server B has its end of the OpenVPN link as 192.168.2.2

On B you need to add a route to 192.168.1.0/24 via A:

route add -net 192.168.1.0/24 gw 192.168.2.1
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  • i added a route back to the client ip.Now i can see incoming traffic but data length of both directions is zero. why?
    – JIA
    May 25, 2015 at 6:31
  • @Benson what do you mean by "data length"? May 25, 2015 at 7:38
  • it's something like this: ack 7802, win 63136, length 0.i've got this far: the client can connec to strongswan running on A and openvpn client on A also successfully established a tunnel with B via openvpn. local traffic originating from A are able to go through the tunnel. But i'm stuck at routing VPN client's web traffic through the openvpn tunnel to the internet. Please suggest a solution.
    – JIA
    May 25, 2015 at 13:49
  • @Benson you need to add appropriate default routes. May 26, 2015 at 20:20

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