[Openswan Users] Cross Site Connectivity

Leonard Wood leonardw at ufl.edu
Thu Feb 25 16:36:21 EST 2016

Thank you for responding.  Site B subnet can change as it’s not required to be that large.  For example purposes, lets now assume Site B private subnet is




From: Nick Howitt [mailto:nick at howitts.co.uk] 
Sent: Thursday, February 25, 2016 4:14 PM
To: Leonard Wood; users at lists.openswan.org
Subject: Re: [Openswan Users] Cross Site Connectivity


Hmm. Generally for VPN's subnets should not overlap at either end of the tunnel or the routing fails. Site B has a massive subnet, - (16,777,216 addresses). Unfortunately subnet A is entirely in Site B's subnet. Does site B need such a big subnet or can site B change to another subnet (either in the range or range but not which is not a good subnet and is, in any case, being used at site C).

The problem you have is that site B sees as local to itself so won't route traffic to Site A down the VPN.


On 25/02/2016 21:00, Leonard Wood wrote:

I have a single Openswan deployment (2.6.38/K4.2.0-27-generic) currently connected to two sites—Site A and Site B.  Let’s call my OpenSwan deployment Site C.


I need to have Site A private subnet communicate with Site B private subnet, and vice versa.


Site A Private Subnet =

Site B Private Subnet =

Site C Private Subnet = (OpenSwan Deployment Subnet)


As of current, I can only communicate to/from Site A from Site C and I can only communicate to/from Site B from Site C. 


Any suggestions how to accomplish cross site connectivity so Site A and communicate with Site B through Site C and vice versa?


Secondly, do you see any security concerns with this approach? Could traffic be intercepted or read in plaintext from my OpenSwan instance (Site C) since it’s essentially acting as MITM?


Many thanks in advance!



Users at lists.openswan.org
Micropayments: https://flattr.com/thing/38387/IPsec-for-Linux-made-easy
Building and Integrating Virtual Private Networks with Openswan:


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