[Openswan Users] openswan with overlapping subnets

[david coleman]

Hello – I have a common problem but I have spent a few hours researching and cannot find the definitive answer.

We are setting up a vpn (site-to-site) to a customer (juniper firewall). We have found that their subnet and our subnet are overlapping.

So our subnet is on 10.180.11.0/24 and theirs is 10.180.0.0/16

We have set up site-to-site vpns using openswan before with success but not with this scenario.

Can we setup the system so that some kind of routing using iptables will make our side look like something that does not overlap like 10.220.11.0/24?

I mean we would leave our internal network alone but put something in openswan/iptables that “translates” or converts how the other side sees our ip address

Diagram:
Their side (10.180.0.0/16) --> Their VPN Firewall (public ip) --> Internet --> our openswan (public) [viewed as 10.220.11.0/24] --> some magic fix to map 10.220.11.0/24 to our “real network” of 10.180.11.0/24 --> our real servers

We actually only have 3 servers to be accessed in our network so if we need to do some setup for each individual ip that is fine

Thanks dave


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