A customer is using the same address space as the company network. I need to connect with Cisco VPN Client to the network of the customer, without affecting local connectivity. To keep all working, I connect from a VM to avoid network addressing collisions. This works, but I'm looking for a way to get rid of the VM.

Is it possible to connect with Cisco VPN Client 4.8 from Windows 7, without changing the 'normal' routing? How to tell specific applications (most importantly: Putty, VNC, mstsc, psql) to resolve their routes to the VPN instead of the default network interface? Have been hearing about SOCKS-proxies, is that something that could be made to work?

I'd be happy to specify more details/context.

  • 3
    The best way to do this, unfortunately, is to do source NAT on both ends of the VPN. So 192.168.1.X/24 on side A is 10.0.0.X/23 on the VPN and 192.16.1.X/24 on side B is 10.0.1.X/23 on the VPN. Dec 10, 2012 at 11:32
  • Both Customer and my network use the full range of the 10.x.x.x address space. I would need the 168-placeholder. So this would be non-trivial to implement. Hoping still for another solution...
    – joepd
    Dec 10, 2012 at 12:17
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    You cannot always know what "specific applications" will call in the background and expect to see the network as they see it... so even if it was possible it would be a problematic idea... Dec 10, 2012 at 12:21
  • @joepd: Then I would suggest mapping addresses on a case-by-case basis. Dec 10, 2012 at 13:07

1 Answer 1


A SOCKS proxy is not a solution to overlapping IPv4 address ranges. How would you figure out whether you meant the local or remote range?

Your best bet would be deploying IPv6 at both sites, solving both this problem and becoming future-ready!

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