[Openswan Users] Site-to-site + OpenVPN

Simon Deziel simon at xelerance.com
Thu May 9 14:05:48 UTC 2013

Right, I wasn't clear in my reply. My recommendation to use IPsec in
transport mode isn't compatible with Neal's recommendation to use
private IPs for the OpenVPN connection.

To use IPsec in transport mode and an OpenVPN tunnel on top, both
endpoint have to use their public IPs for the 2 VPNs.

In that scenario, since OpenVPN will be bound to the public IP too I'd
recommend to firewall it with something like this to require IPsec:

  iptables -A INPUT -p udp --dport 1399 -m policy --dir in \
           --proto esp -j ACCEPT
  iptables -A INPUT -p udp --dport 1399 -j DROP

Adapt for a TCP based OpenVPN configuration.


On 13-05-08 07:13 PM, Leto wrote:
> you cannot use transport in this scenario unless you double NAT it
> sent from a tiny device 
> On 2013-05-08, at 18:39, Simon Deziel <simon at xelerance.com> wrote:
>> Hi,
>> On 13-05-08 05:13 PM, Neal Murphy wrote:
>>> On Wednesday, May 08, 2013 04:02:34 PM Damir Reic wrote:
>>>> Hello,
>>>> this is theoretical question:
>>>> Let's say i have 2 servers, intermediary server and destination openvpn
>>>> server. If i establish site-to-site VPN with openswan between those 2
>>>> servers, can i let's say use this tunnel to tunnel openvpn requests and
>>>> whole openvpn traffic to destination server (both server have public IP).
>>> It's not so theoretical. It's basically what certain governments and 
>>> militaries do (an encrypted tunnel in an encrypted tunnel using different 
>>> technologies); the same fault is not likely to be found in both.
>>> I believe OpenVPN uses UDP packets (port 1194 by default); it's ordinary IP 
>>> traffic. If you set up IPSEC with the proper LAN addresses at each end and use 
>>> the private (or internal) server address, then it should work. Don't configure 
>>> OpenVPN to use the servers' public addresses, and be sure to use different 
>>> encryption algorithms.
>> I'd also recommend using transport mode instead of tunnel mode because
>> of the lower overhead in terms of payload.
>> Simon
>> _______________________________________________
>> Users at lists.openswan.org
>> https://lists.openswan.org/mailman/listinfo/users
>> Micropayments: https://flattr.com/thing/38387/IPsec-for-Linux-made-easy
>> Building and Integrating Virtual Private Networks with Openswan:
>> http://www.amazon.com/gp/product/1904811256/104-3099591-2946327?n=283155

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